Long was born on August 30, 1893, near Winnfield, a small town in the north-central part of Louisiana and the seat of Winn Parish. He was the son of Huey Pierce Long, Sr. (1852–1937) and the Caledonia Palestine Tison (1860–1913), and the seventh of the couple's nine surviving children. At the time of his youth, Winn Parish was a deeply impoverished region whose people, mostly modest Southern Baptists were known for their cantankerous stubbornness and for being outsiders in Louisiana's political system. During the Civil War, Winn Parish had been a stronghold of Unionism in an otherwise solidly Confederate state, in the 1890s a bastion of the Populist Party, and in 1912 the majority in Winn Parish had voted for the Socialist Party's presidential candidate, Eugene Debs. The degree of poverty in Winn Parish was extreme, but in general Louisiana was a very poor state, with the 1930 census showing that one-fifth of white Louisianans were illiterate, with rates for black Louisianans being much higher. As someone who was born and grew up in Winn Parish, Long inherited all of the resentments of its people against the elite in Baton Rouge who ruled Louisiana. And while Long often told his followers that he came from the lowest possible social and economic stratum, the reality is that Long's family were well-off compared to others in the largely destitute community of Winnfield.

For one thing, Jeansonne notes that Long never faced a serious election that hinged on questions of race or racism, largely because after the Louisiana Constitution of 1898 was ratified, "race was an irrelevant political issue" and black Louisianans "were segregated, ghettoized, ignored." This means that Long never had to actively discuss the subject of race. For another thing, Jeansonne argues that it is fallacious to ascribe to Long views of racial egalitarianism simply because he was not as racist as some of his peers. Finally, as Jeansonne points out, if part of the point of Long's program was to help black Louisianans, it seems likely that Long would have actively attempted to reach out to and enfranchise more black voters so as to secure their political support. This, however, was not the case; in fact, during Long's tenure as governor, the number of registered black voters actually decreased.

During his time at Winnfield High School, Long proved himself to be a capable debater, and at a statewide debating competition in Baton Rouge, he won a debating scholarship to Louisiana State University (LSU). However, because the award did not include money for textbooks or living expenses, he was unable to attend. Long would long regret that he had been unable to pursue an education at LSU. Instead of immediately pursuing a higher education, he spent most of the early 1910s as a traveling salesman, selling books, canned goods and patent medicines, as well as working as an auctioneer.

In September 1911, when sales jobs grew scarce during World War I, Long attended seminary classes at Oklahoma Baptist University in Shawnee, Oklahoma at the urging of his mother, a devout Baptist. Living with his brother, George, Long attended the school for only a semester, and barely went to any lectures. After a while, Long decided he was not suited to preaching and instead began to focus on law. Borrowing one hundred dollars from his brother (which he later lost playing roulette in Oklahoma City), Long briefly attended the University of Oklahoma College of Law in Norman, Oklahoma for a semester in 1912. To earn money while in the Norman area, he worked for the Dawson Produce Company, selling produce while studying law part-time. Of the four classes that Long took, he received one incomplete and three C's. He later confessed that he "didn't learn much law there" because there was "too much excitement, all those gambling houses and everything." After working as a traveling salesman for a few more years, Long enrolled in Tulane University Law School in New Orleans in the fall of 1914. After only a year at Tulane, he convinced a board to let him take the state bar exam, which he passed.

In 1913, Long married Rose McConnell. She was a stenographer who had won a baking contest which he promoted to sell "Cottolene", one of the most popular of the early vegetable shortenings to come on the market. The two began a two and a half year courtship that finally ended with their marriage on April 12, 1913 in Memphis, Tennessee. The wedding took place at the Grayoso Hotel; Huey, who was broke at the time, had to borrow $10 from his fiancée to pay the officiant's services. The Longs had a daughter, also named Rose, and two sons: Russell B. Long, who subsequently became a long-term U.S. senator, and Palmer Reid Long (1921–2010), who became a Shreveport oilman. Long wrote in his 1933 autobiography, Every Man a King "If the loyalty of a wife and children could have elevated anyone in public life, I had that for complete success."

In 1915, Long began a private practice in Winnfield. Later, in Shreveport, he spent ten years representing small plaintiffs against large businesses, including workers' compensation cases. He often said proudly that he never took a case against a poor man, and he once famously—and successfully—defended a widow against the Winnfield Bank (the President of which was Long's uncle George).

In 1918, Long entered into the race to serve on the three-seat Louisiana Railroad Commission. According to william Ivy Hair, Long's political message which he used to campaign for a seat on the commission:

In the gubernatorial election of 1920, he campaigned prominently for John M. Parker, and today Long is often credited with helping Parker to win in the northern Louisiana parishes. However, after Parker was elected to the gubernatorial office, the two became bitter rivals. This break was largely the result of Long having demanded that Parker declare the state's oil pipelines to be public utilities and Parker having refused to do so. In particular, Long was horrified and became furious when Parker allowed the oil companies the legal team of Standard Oil to assist in the writing of the state's severance tax laws—laws that decreed how much money corporations such as Standard Oil had to pay the state for the extraction of natural resources. Because the governor was willing to go along with companies like Standard Oil, Huey began calling Parker the "chattel" of the corporations. After butting heads, Parker eventually tried to have Huey ousted from his position on the Louisiana Railroad Commission in 1921, although he was unable to do so.

By 1922, the Railroad Commission had been renamed "the Public Service Commission", on which Long retained a seat. He soon dedicated his life to adding "new Energy and independence into the agency", as well as increasing the commission's (and, by extension, his own) power. In 1922, Long won a lawsuit against the Cumberland Telephone & Telegraph Company for unfair rate increases, Long successfully argued the case on appeal before the United States Supreme Court resulting in cash refunds totaling $440,000 being sent to 80,000 overcharged customers. After the case, Chief Justice william Howard Taft described Long as one of the best legal minds he had ever encountered.

Long ran for governor of Louisiana in the election of 1924, attacking outgoing Governor Parker, Standard Oil, and the established political hierarchy both locally and statewide. In that campaign, he became one of the first Southern politicians to use radio addresses and sound trucks. Long also began wearing a distinctive white linen suit. He came in third and although he and another candidate had privately opposed the powerful Ku Klux Klan, a third candidate had openly supported it. The Klan's prominence in Louisiana was the primary issue of the campaign. Long cited rain on election day as suppressing voter turnout among his base in rural north Louisiana, where voters were unable to reach the polls on dirt roads that had turned to mud.

Instead, Long was reelected later in the year to the Public Service Commission. His former law partner and political ally, Harvey Fields, a former state senator for Union and Morehouse parishes, succeeded Long on the PSC, with Service from 1927 to 1936.

In general, the novelists have portrayed Long's rise to power as a justifiable popular reaction against the selfish policies pursued by the dominant economic interests prior to 1928. They speculate the degree his extremism reflected an overreaction to his enemies, or sprang inevitably from class conflict in the state. They all try to explain why Long enjoyed majority support in Louisiana, both during and after his lifetime.

In 1929, Long called a special session of both houses of the legislature to enact a new five-cent per barrel "occupational license tax" on production of refined oil, to help fund his social programs. The bill met with fierce opposition from the state's oil interests. Opponents in the legislature, led by freshman lawmakers Cecil Morgan of Shreveport and Ralph Norman Bauer of Franklin in St. Mary Parish, moved to impeach Long on charges ranging from blasphemy to abuses of power, bribery, and the misuse of state funds. Long tried to cut the session short, but after an infamous brawl that spilled across the State Legislature on what was known as "Bloody Monday," the Legislature voted to remain in session and proceed with the impeachment.

Leading novelists have explored the regime Long created. Garry Boulard believed him to be the inspiration for Buzz Windrip in Sinclair Lewis's It Can't Happen Here, calling the work "the most chilling and uncanny treatment of Huey by a writer". Lewis, a liberal who in 1930 had won the Nobel Prize in literature, portrayed a genuine American dictator on the Hitler model. The lead character of It Can't Happen Here is a populist, big business-bashing senator Buzz Windrip who wins the 1936 election by promising every American family $5,000 per year. Starting in 1936 the WPA, a New Deal agency, performed the theater version across the country.

In October 1931, Lieutenant Governor Cyr, by then Long's avowed enemy, argued that the Senator-elect could no longer remain governor. Cyr declared himself the state's legitimate governor. In response, Long ordered state National Guard troops to surround the State Capitol and fended off Cyr's proposed "coup d'état."

Long's free textbooks, school-building program, and school busing improved and expanded the public education system. His night schools taught 100,000 adults to read. He expanded funding for LSU, tripled enrollment, lowered tuition, and established scholarships for low-income students. He sometimes befriended persons in need. In 1932 a young Pap Dean, later political Cartoonist with the Shreveport Times, wrote to Long after hearing him speak in Dean's native Colfax to explain that Dean's college funds had been lost in a bank closing. Long helped Dean procure financial aid to attend LSU, from which he graduated in 1937.

Long's first autobiography, Every Man a King, was published in 1933 and priced to be affordable by poor Americans. Long laid out his plan to redistribute the nation's wealth. His second book, My First Days in the White House, was published posthumously. In it he describes his presidential ambitions for 1936.

Hamilton Basso wrote two novels looking at Long, Cinnamon Seed (1934) and Sun in Capricorn (1942). Perry (2004) says Basso was a slashingly witty critic of the moonlight and magnolia Romanticism of the Old South that dominated the Southern mind before 1920. Like many proponents of a New South, he wanted modernizers to take over. Cinnamon Seed's Harry Brand incorporates more details from the historical Long than any other fictional portrayal does, and much of the novel is so lightly fictionalized that only a single letter separates the names of characters and places from their real-life counterparts. Brand is a representative of the grasping and vulgar kind of new leadership which has rightly understood that the values of the Old South are played out but has replaced them with nothing but ambition and cunning. He is a greedy climber, not a demonic leader of the masses, and in fact he is ultimately not much more than an obnoxious and sticky-fingered lout, the kind who spits tobacco juice on the marble floors of his predecessors and pockets the ashtrays. In portraying his Long figure this way, Basso finds himself between the stools, critical of the spent aristocrats who cannot imagine a modern South, but disgusted also by the figures who represent the wrong kind of newness, the kind of modern South that comes to be if its development is left to default.

In the Hearts of Iron video game series mod, Kaiserreich, Huey Long is the leader of the America First Party, a party that combines the ideals of American nationalism and slight leftist policies, but is also heavily anti-Syndicalist. Huey Long is not assassinated in 1935 in this timeline, allowing him to run for the 1936 presidency under the aforementioned AFP. If he loses the election, or if there is a leftist uprising within America, Long and the AFP will break away from the United States to form the "American Union State", a radical insurgent faction intent on destroying the syndicalist threat.

Written with the goal of hurting Long's chances in the 1936 election, Lewis's novel outfits President Berzelius Windrip with a private militia, concentration camps, and a chief of staff who sounds like Nazi propagandist Joseph Goebbels. Lewis also outfits Windrip with a racist ideology completely alien to Long and a Main Street conservatism he also never embraced. Ultimately, Windrip is a venal and cynical showman who plays to the conformist resentments Lewis diagnosed in Main Street and Babbitt. Perry (2004) argues that the key weakness of the novel is not that he decks out American politicians with sinister European touches, but that he finally conceives of fascism and totalitarianism in terms of traditional American political Models rather than seeing them as introducing a new kind of society and a new kind of regime. Windrip is less a Nazi than a con-man and manipulator who knows how to appeal to people's desperation, but neither he nor his followers are in the grip of the kind of world-transforming ideology like Hitler's National Socialism.

John Dos Passos's Number One (1943) looks not at the politics of mass brutality whipped up by manipulative demagogues, but at the gradual ebbing away of Long's idealist convictions under the pressure of a thousand expedient compromises and betrayals in the name of institutional necessity.

Long inspired numerous other novelists. Adria Locke Langley's 1945 novel A Lion Is in the Streets, and its 1953 film adaption starring James Cagney as the charismatic and ambitious but also unscrupulous Huey Long-like populist Politician Hank Martin has often been compared to All the King's Men. Bruce Sterling's Distraction features a colorful and dictatorial Louisiana governor named "Green Huey". Harry Turtledove's American Empire trilogy drew parallels between Confederate President Jake Featherston's populist, dictatorial style of rule and Long's governorship of Louisiana. In this trilogy, Long was assassinated on orders from Featherston when he refused to side with the Confederate ruling party (though several years later than in reality). In Barry N. Malzberg's short story "Kingfish", published in the Alternate Presidents anthology, Long survives his assassination, to be elected President in 1936 with the help of John Nance Garner, and both men conspire to assassinate Hitler prior to the start of World War II. In Donald Jeffries' 2007 novel The Unreals, there is a scene featuring an imaginary meeting where FDR and other important Depression era figures are plotting the assassination of Senator Long.

Robert Penn Warren's Pulitzer prize-winning novel All the King's Men (1946) is the centerpiece of American political fiction. Warren charted the corruption of an idealistic Politician Willie Stark, almost as much Philosopher as Politician. Warren did not encourage association of his character with Long and told Charles Bohner in a 1964 interview, "Willie Stark was not Huey Long. Willie was only himself, whatever that self turned out to be." Nevertheless, popular and critical opinion has held the parallels between Stark and Long to be very strong (particularly the general arc of the career: a failed bid for Governor in the mid-1920s, successful election to the governorship, and subsequent assassination); Warren's spellbinding Willie Stark has been for almost six decades Long's well-known fictional embodiment, based on the novel and well-received 1949 movie, earning Best Picture, Best Actor and Best Supporting Actress from the Academy Awards.

Long's death did not end the political strength of the Long family. His widow, Rose McConnell Long, was appointed to replace him in the Senate, and his son Russell B. Long was elected to the Senate in 1948, and served until his retirement in 1987. In addition to Long's brother Earl K. Long becoming governor, brother Julius Long was a Winn Parish District Attorney and brother George S. Long was elected to Congress in 1952. Long's younger sister, Lucille Long Hunt (1898–1985) of Ruston, was the mother of Future Public Service Commissioner John S. Hunt, II (1928–2001), of Monroe.

Warren's novel was the basis of two motion pictures, a 1949 film and a more recent 2006 film, and the 1981 opera Willie Stark by American Composer Carlisle Floyd. The 1949 film won three Oscars, including Best Picture and Best Actor for Broderick Crawford, playing the Long role.

The next Republican gubernatorial candidate, Harrison Bagwell, a Baton Rouge attorney who supported Dwight Eisenhower for U.S. President, also polled 4 percent of the vote in his 1952 contest against Democrat Robert F. Kennon, a leader of the anti-Long forces.

The political machine Long established was weakened by his death, but it remained a powerful force in state politics until the election of 1960. Pockets of it persisted into the 21st century. The Long platform of social programs and populist rhetoric created the state's main political division. In every state election until 1960, the main factions were organized along pro-Long and anti-Long lines. For several decades after his death, Long's personal political style inspired imitation among Louisiana politicians who borrowed his colorful speaking style, vicious Verbal attacks on opponents, and promises of social programs. His brother Earl Kemp Long later inherited Long's political machine. Using his platform and rhetorical style, Earl Long became governor in 1939 following the resignation of Richard Leche and was elected to subsequent terms in 1948 and 1956.

Long's life has held continuing fascination. In 1970, the biography Huey Long by T. Harry Williams won both the Pulitzer Prize and the National Book Award in category History and Biography. Alan Brinkley won the latter award in 1983 for Voices of Protest: Huey Long, Father Coughlin and the Great Depression, which describes Long's brief but vast popularity early in the 1930s.

In popular music, singer-songwriter Randy Newman featured Long in two songs on the 1974 album Good Old Boys (Reprise). "Every Man a King", originally written and recorded by Long and Castro Carazo, is followed by "Kingfish". Sung from the point of view of Long, "Kingfish" discusses his popularity in his prime, the building of the Airline Highway, and refers to "The Kingfish" as "friend of the working man"‍—‌an allusion to Long's unwavering popularity amongst the working classes. It attributes the reason for this to his populist ideologies:

Two made-for-TV docudramas about Long have also been produced: The Life and Assassination of the Kingfish (1977), starring Ed Asner, and the fictionalized Kingfish: A Story of Huey P. Long (1995, TNT), starring John Goodman.

In 1993, Long, along with his brother Earl, was inducted posthumously into the Louisiana Political Museum and Hall of Fame in Winnfield. In the same ceremony, his son Russell, then still living, was also among the 13 original inductees.

After Earl Long's death, John McKeithen and Edwin Edwards appeared as heirs to the Long tradition. Most recently, Claude "Buddy" Leach ran a populist campaign in the Louisiana gubernatorial election of 2003 that some observers compared to Huey Long's. Louisiana Public Service Commissioner Foster Campbell tried the same approach without success in the 2007 jungle primary, although State Rep. John Bel Edwards was elected governor in 2015 espousing many of the same populist positions as Long, McKeithen and Edwin Edwards.

Other more distant relatives, including Gillis william Long and Speedy O. Long represented Louisiana in the U.S. Congress, while Jimmy D. Long of Natchitoches Parish served for 32 years in the Louisiana House. As of 2010, Jimmy Long's younger brother Gerald Long holds the distinction of being the only current Long in public office and the first Republican among the Long Democratic dynasty. Twelve members of the Long family have held elected office.

Within the dominant Louisiana Democratic party, Long set in motion two durable factions—"pro-Long" and "anti-Long"—which diverged meaningfully in terms of policies and voter support. A family dynasty emerged: his brother Earl Long was elected lieutenant-governor in 1936, governor in 1948 and 1956. Typically anti-Longite candidates would promise to continue popular social services delivered in Long's administration and criticized Longite corruption without directly attacking Long himself. Long's son, Russell B. Long, was a U.S. senator from 1948 to 1987. As chairman of the Senate Finance Committee, Russell Long shaped the nation's tax laws. He was an advocate of low Business taxes, but also passed the Earned Income Credit and other tax legislation beneficial to the poor and working people.