Heinlein was born on July 7, 1907 to Rex Ivar Heinlein (an accountant) and Bam Lyle Heinlein, in Butler, Missouri. He was a 6th-generation German-American: a family tradition had it that Heinleins fought in every American war starting with the War of Independence.

In 1929, Heinlein married Elinor Curry of Kansas City in Los Angeles, and their marriage lasted about a year. His second marriage in 1932 to Leslyn MacDonald (1904–1981) lasted for 15 years. MacDonald was, according to the testimony of Heinlein's Navy buddy, Rear Admiral Cal Laning, "astonishingly intelligent, widely read, and extremely liberal, though a registered Republican," while Isaac Asimov later recalled that Heinlein was, at the time, "a flaming liberal". (See section: Politics of Robert Heinlein.)

However, he was skeptical about Freudianism, especially after a struggle with an Editor who insisted on reading Freudian sexual symbolism into his Juvenile novels. Heinlein was fascinated by the social credit movement in the 1930s. This is shown in Beyond This Horizon and in his 1938 novel For Us, The Living: A Comedy of Customs, which was finally published in 2003, long after his death.

Heinlein also served aboard the destroyer USS Roper in 1933 and 1934, reaching the rank of lieutenant. His brother, Lawrence Heinlein, served in the U.S. Army, the U.S. Air Force, and the Missouri National Guard, and he rose to the rank of major general in the National Guard.

Heinlein's political positions shifted throughout his life. Heinlein's early political leanings were to the liberal. In 1934, he worked actively for the Democratic campaign of Upton Sinclair for Governor of California. After Sinclair lost, Heinlein became an anti-Communist Democratic Activist. He made an unsuccessful bid for a California State Assembly seat in 1938. Heinlein's first novel, For Us, The Living (written 1939), consists largely of speeches advocating the Social Credit system, and the early story "Misfit" (1939) deals with an organization that seems to be Franklin D. Roosevelt's Civilian Conservation Corps translated into outer space.

For Heinlein, personal liberation included sexual liberation, and free love was a major subject of his writing starting in 1939, with For Us, The Living. During his early period, Heinlein's writing for younger readers needed to take account of both editorial perceptions of sexuality in his novels, and potential perceptions among the buying public; as critic william H. Patterson has put it, his dilemma was "to sort out what was really objectionable from what was only excessive over-sensitivity to imaginary librarians". By his middle period, sexual freedom and the elimination of sexual jealousy were a major theme of Stranger in a Strange Land (1961), in which the progressively minded but sexually conservative reporter, Ben Caxton, acts as a dramatic foil for the less parochial characters, Jubal Harshaw and Valentine Michael Smith (Mike). Another of the main characters, Jill, is homophobic.

Heinlein's fiction of the 1940s and 1950s, however, began to espouse conservative views. After 1945, he came to believe that a strong world government was the only way to avoid mutual nuclear annihilation. His 1949 novel Space Cadet describes a Future scenario where a military-controlled global government enforces world peace. Heinlein ceased considering himself a Democrat in 1954. He was among those who in 1968 signed a pro-Vietnam War ad in Galaxy Science Fiction.

Race was a central theme in some of Heinlein's fiction. The most prominent and controversial Example is Farnham's Freehold, which casts a white family into a Future in which white people are the slaves of cannibalistic black rulers. In the 1941 novel Sixth Column (also known as The Day After Tomorrow), a white resistance movement in the United States defends itself against an invasion by an Asian fascist state (the "Pan-Asians") using a "super-science" Technology that allows ray weapons to be tuned to specific races. The book is sprinkled with racist slurs against Asian people, and blacks and Hispanics are not mentioned at all. The idea for the story was pushed on Heinlein by Editor John W. Campbell, and Heinlein wrote later that he had "had to re-slant it to remove racist aspects of the original story line" and that he did not "consider it to be an artistic success." However, the novel prompted a heated debate in the scientific community regarding the plausibility of developing ethnic bioweapons.

As the war wound down in 1945, Heinlein began re-evaluating his career. The atomic bombings of Hiroshima and Nagasaki, along with the outbreak of the Cold War, galvanized him to write nonfiction on political topics. In addition, he wanted to break into better-paying markets. He published four influential short stories for The Saturday Evening Post magazine, leading off, in February 1947, with "The Green Hills of Earth". That made him the first science fiction Writer to break out of the "pulp ghetto". In 1950, the movie Destination Moon—the documentary-like film for which he had written the story and scenario, co-written the script, and invented many of the effects—won an Academy Award for special effects. Also, he embarked on a series of Juvenile novels for the Charles Scribner's Sons publishing company that went from 1947 through 1959, at the rate of one book each autumn, in time for Christmas presents to teenagers. He also wrote for Boys' Life in 1952.

Heinlein had used topical materials throughout his Juvenile series beginning in 1947, but in 1959, his novel Starship Troopers was considered by the editors and owners of Scribner's to be too controversial for one of its prestige lines, and it was rejected.

As his second wife's alcoholism gradually spun out of control, Heinlein moved out and the couple filed for divorce. Heinlein's friendship with Virginia turned into a relationship and on October 21, 1948—shortly after the decree nisi came through—they married in the town of Raton, New Mexico shortly after having set up housekeeping in Colorado. They would remain married until Heinlein's death.

Heinlein is usually identified, along with Isaac Asimov and Arthur C. Clarke, as one of the three masters of science fiction to arise in the so-called Golden Age of science fiction, associated with John W. Campbell and his magazine Astounding. In the 1950s he was a leader in bringing science fiction out of the low-paying and less prestigious "pulp ghetto". Most of his works, including short stories, have been continuously in print in many languages since their initial appearance and are still available as new paperbacks decades after his death.

The term "pay it forward", though it was already in occasional use as a quotation, was popularized by Robert A. Heinlein in his book Between Planets, published in 1951:

Heinlein has had a nearly ubiquitous influence on other science fiction Writers. In a 1953 poll of leading science fiction authors, he was cited more frequently as an influence than any other modern Writer. Critic James Gifford writes that "Although many other Writers have exceeded Heinlein's output, few can claim to match his broad and seminal influence. Scores of science fiction Writers from the prewar Golden Age through the present day loudly and enthusiastically credit Heinlein for blazing the trails of their own careers, and shaping their styles and stories."

Spider Robinson, a colleague, friend, and admirer of Heinlein, wrote Variable Star, based on an outline and notes for a Juvenile novel that Heinlein prepared in 1955. The novel was published as a collaboration, with Heinlein's name above Robinson's on the cover, in 2006.

In books written as early as 1956, Heinlein dealt with Incest and the sexual nature of children. Many of his books including Time for the Stars, Glory Road, Time Enough for Love, and The Number of the Beast dealt explicitly or implicitly with Incest, sexual feelings and relations between adults and children, or both. The treatment of these themes include the romantic relationship and eventual marriage, once the girl becomes an adult via time-travel, of a 30-year-old Engineer and an 11-year-old girl in The Door into Summer or the more overt intra-familial Incest in To Sail Beyond the Sunset and Farnham's Freehold. Peers such as L. Sprague de Camp and Damon Knight have commented critically on Heinlein's portrayal of Incest and pedophilia in a lighthearted and even approving manner.

Heinlein was a mentor to Ray Bradbury, giving him help and quite possibly passing on the concept, made famous by the publication of a letter from him to Heinlein thanking him. In Bradbury's novel Dandelion Wine, published in 1957, when the main character Douglas Spaulding is reflecting on his life being saved by Mr. Jonas, the Junkman:

The Heinleins formed the small "Patrick Henry League" in 1958, and they worked in the 1964 Barry Goldwater Presidential campaign.

Heinlein decisively ended his Juvenile novels with Starship Troopers (1959), a controversial work and his personal riposte to leftists calling for President Dwight D. Eisenhower to stop nuclear testing in 1958. "The "Patrick Henry" ad shocked 'em," he wrote many years later. "Starship Troopers outraged 'em." Starship Troopers is a coming-of-age story about duty, citizenship, and the role of the military in society. The book portrays a society in which suffrage is earned by demonstrated willingness to place society's interests before one's own, at least for a short time and often under onerous circumstances, in government service; in the case of the protagonist, this was military Service.

From about 1961 (Stranger in a Strange Land) to 1973 (Time Enough for Love), Heinlein explored some of his most important themes, such as individualism, libertarianism, and free expression of physical and emotional love. Three novels from this period, Stranger in a Strange Land, The Moon Is a Harsh Mistress, and Time Enough for Love, won the Libertarian Futurist Society's Prometheus Hall of Fame Award, designed to honor classic libertarian fiction. Jeff Riggenbach described The Moon Is a Harsh Mistress as "unquestionably one of the three or four most influential libertarian novels of the last century".

In 1962, Oberon Zell-Ravenheart (then still using his birth name, Tim Zell) founded the Church of All Worlds, a Neopagan religious organization modeled in many ways after the treatment of religion in the novel Stranger in a Strange Land. This spiritual path included several ideas from the book, including non-mainstream family structures, social libertarianism, water-sharing rituals, an acceptance of all religious paths by a single tradition, and the use of several terms such as "grok", "Thou art God", and "Never Thirst". Though Heinlein was neither a member nor a promoter of the Church, there was a frequent exchange of correspondence between Zell and Heinlein, and he was a paid subscriber to their magazine, Green Egg. This Church still exists as a 501(C)(3) religious organization incorporated in California, with membership worldwide, and it remains an active part of the neopagan community today.

As Heinlein's increasing success as a Writer resolved their initial financial woes, they had a house custom built with various innovative features, later described in an article in Popular Mechanics. In 1965, after various chronic health problems of Virginia's were traced back to altitude sickness, they moved to Santa Cruz, California, at sea level, while they were building a new residence in the adjacent village of Bonny Doon, California. Robert and Virginia designed and built their California house themselves, which is in a circular shape. Previously they had also designed and built their Colorado house.

Heinlein considered himself a libertarian; in a letter to Judith Merril in 1967 (never sent) he said, "As for libertarian, I've been one all my life, a radical one. You might use the term "philosophical anarchist" or "autarchist" about me, but "libertarian" is easier to define and fits well enough."

In the mid-1970s, Heinlein wrote two articles for the Britannica Compton Yearbook. He and Ginny crisscrossed the country helping to reorganize blood donation in the United States in an effort to assist the system which had saved his life. At science fiction conventions to receive his autograph, fans would be asked to co-sign with Heinlein a beautifully embellished pledge form he supplied stating that the recipient agrees that they will donate blood. He was the guest of honor at the Worldcon in 1976 for the third time at MidAmeriCon in Kansas City, Missouri. At that Worldcon, Heinlein hosted a blood drive and donors' reception to thank all those who had helped save lives. While vacationing in Tahiti in early 1978, he suffered a transient ischemic attack. Over the next few months, he became more and more exhausted, and his health again began to decline. The Problem was determined to be a blocked carotid artery, and he had one of the earliest known carotid bypass operations to correct it. Heinlein and Virginia had been smokers, and smoking appears often in his fiction, as do fictitious strikable self-lighting cigarettes.

The Science Fiction Writers of America named Heinlein its first Grand Master in 1974, presented 1975. Officers and past Presidents of the Association select a living Writer for lifetime achievement (now annually and including fantasy literature).

After a seven-year hiatus brought on by poor health, Heinlein produced five new novels in the period from 1980 (The Number of the Beast) to 1987 (To Sail Beyond the Sunset). These books have a thread of Common characters and time and place. They most explicitly communicated Heinlein's philosophies and beliefs, and many long, didactic passages of dialog and exposition deal with government, sex, and religion. These novels are controversial among his readers and one critic, David Langford, has written about them very negatively. Heinlein's four Hugo awards were all for books written before this period.

The 1982 novel Friday, a more conventional adventure story (borrowing a character and backstory from the earlier short story Gulf, also containing suggestions of connection to The Puppet Masters) continued a Heinlein theme of expecting what he saw as the continued disintegration of Earth's society, to the point where the title character is strongly encouraged to seek a new life off-planet. It concludes with a traditional Heinlein note, as in The Moon Is a Harsh Mistress or Time Enough for Love, that freedom is to be found on the frontiers.

The 1984 novel Job: A Comedy of Justice is a sharp satire of organized religion. Heinlein himself was agnostic.

Asked to appear before a Joint Committee of the U.S. House and Senate that year, he testified on his belief that spin-offs from space Technology were benefiting the infirm and the elderly. Heinlein's surgical treatment re-energized him, and he wrote five novels from 1980 until he died in his sleep from emphysema and heart failure on May 8, 1988.

Several Heinlein works have been published since his death, including the aforementioned For Us, The Living as well as 1989's Grumbles from the Grave, a collection of letters between Heinlein and his editors and agent; 1992's Tramp Royale, a travelogue of a southern hemisphere tour the Heinleins took in the 1950s; Take Back Your Government, a how-to book about participatory democracy written in 1946; and a tribute volume called Requiem: Collected Works and Tributes to the Grand Master, containing some additional short works previously unpublished in book form. Off the Main Sequence, published in 2005, includes three short stories never before collected in any Heinlein book (Heinlein called them "stinkeroos").

Main-belt asteroid 6312 Robheinlein (1990 RH4), discovered on September 14, 1990 by H. E. Holt, at Palomar was named after him.

There is no lunar feature named explicitly for Heinlein, but in 1994 the International Astronomical Union named Heinlein crater on Mars in his honor.

The name Starship Troopers was licensed for an unrelated, B movie script called Bug Hunt at Outpost Nine, which was then retitled to benefit from the book's credibility. The resulting film, entitled Starship Troopers (1997), which was written by Ed Neumeier and directed by Paul Verhoeven, had little relationship to the book, beyond the inclusion of character names, the depiction of space marines, and the concept of suffrage earned by military Service. Fans of Heinlein were critical of the movie, which they considered a betrayal of Heinlein's philosophy, presenting the society in which the story takes place as fascist.

The Science Fiction and Fantasy Hall of Fame inducted Heinlein in 1998, its third class of two deceased and two living Writers and editors.

In 2001 the United States Naval Academy created the Robert A. Heinlein Chair In Aerospace Engineering.

The Heinlein society also established the Robert A. Heinlein Award in 2003 "for outstanding published works in science fiction and technical writings to inspire the human exploration of space."

Heinlein was also a guest commentator for Walter Cronkite during Neil Armstrong and Buzz Aldrin's Apollo 11 moon landing. He remarked to Cronkite during the landing that, "This is the greatest event in human history, up to this time. This is—today is New Year's Day of the Year One." Businessman and Entrepreneur Elon Musk says that Heinlein's books have helped inspire his career.

In 2016, after an intensive online campaign to win a vote for the opening, Heinlein was inducted into the Hall of Famous Missourians. His bronze bust, created by Kansas City Sculptor E. Spencer Schubert, is on permanent display in the Missouri State Capitol in Jefferson City.