Durant was born on September 29, 1988, in Washington, D.C., to Wanda (née Durant) and Wayne Pratt. When Durant was an infant, his father deserted the family; Wanda and Wayne eventually divorced, and Durant's grandmother Barbara Davis helped raise him. By age 13, his father re-entered his life and traveled the country with him to basketball tournaments. Durant has one sister, Brianna, and two brothers, Tony and Rayvonne.

For the 2006–07 college season, Durant—who had grown to 6 ft 9 in (2.06 m)—averaged 25.8 points, 11.1 rebounds, and 1.3 assists per game for the Texas Longhorns as a student at the University of Texas. The Longhorns finished the year with a 25–10 record overall and a 12–4 record in conference. Awarded a fourth seed in the NCAA Tournament, Texas won their first round match-up against New Mexico State but were upset in the second round by USC despite a 30-point and 9-rebound performance from Durant. For his outstanding play, Durant was recognized as the unanimous national player of the year, winning the John R. Wooden Award, the Naismith College Player of the Year Award, and all eight other widely recognized honors and awards. This made Durant the first freshman to win any of the national player of the year awards. On April 11, he officially declared for the NBA draft. His #35 jersey was later retired by the Longhorns.

In February 2007, Durant received an invitation to the United States national team training camp. Despite a strong performance, he was cut from the team when its roster was trimmed to its twelve-player limit. Coach Mike Krzyzewski cited the experience of the remaining players as the deciding factor in making the cut. Durant was finally selected to the national team at the 2010 FIBA World Championship and became their leader as other All-Stars were unavailable, a role he downplayed. At the tournament, he led Team USA to its first FIBA World Championship since 1994, earning MVP honors in the process. His final averages for the competition were 22.8 points, 6.1 rebounds, 3.1 assists, and 1.4 steals per game in nine games.

During the 2009–10 season, Durant was selected to his first NBA All-Star Game. Behind his play, the Thunder improved their record by 27 wins from the previous year and defied expectations to make the playoffs. With a scoring average of 30.1 points per game, he became the youngest NBA scoring champion and was selected to his first All-NBA team. In his playoff debut, he scored 24 points in a Game 1 loss against the Los Angeles Lakers. Oklahoma City would go on to lose the series in six games, but the team's performance led many analysts to label them as an upcoming title contender.

Early in Durant's career, he was criticized for his slim build, defense, and passing. Over time, he grew as a playmaker, increasing his assist numbers every year from 2010 to 2014; however, his overall vision still lagged behind the league's best passers'. He also showed defensive improvement, with opponents averaging just .62 points per isolation play against him in 2014, the best success rate for defensive players who faced at least 100 isolations that season. Upon going to Golden State, he developed into a more reliable off-ball defender and rim protector, and he received consideration for the Defensive Player of the Year Award in 2018.

On February 19 of the lockout-shortened 2011–12 season, Durant recorded his first career 50-point game, scoring 51 points against the Denver Nuggets. At the All-Star Game, he scored 36 points and was awarded the NBA All-Star Game Most Valuable Player Award. He finished the year with a scoring average of 28 points per game, representing his third straight scoring title. Behind his play, the Thunder won 47 games and entered the playoffs as the Western Conference's second seed. In Game 1 of the first round against the Mavericks, Durant hit a game-winner with 1.5 seconds remaining. Oklahoma City would go on to defeat Dallas, the Lakers, and the San Antonio Spurs before losing to the Miami Heat in the Finals. For the NBA Finals, Durant led all players with 30.6 points per game, doing so on a 54.8 shooting rate.

At the 2012 Olympics, Durant set the record for total points scored in an Olympic basketball tournament. With averages of 19.5 points, 5.8 rebounds, 2.6 assists, and 1.6 steals per game, he helped the national team go undefeated en route to a gold medal. In the tournament's final game, he led all scorers with 30 points.

Throughout his career, Durant has participated in philanthropic causes. In 2013, he pledged $1 million to the American Red Cross for the victims of the 2013 Moore tornado. His generosity inspired the Thunder and Nike to match his donation. He is also a spokesperson for the Washington, D. C. branch of P'Tones Records, a nationwide non-profit after-school music program.

Less than a month before the start of the 2014 FIBA Basketball World Cup, Durant announced that he would be dropping out of the competition, citing mental and physical exhaustion as reasons for his departure. He rejoined Team USA in 2016 for the Olympics, where he led them to a gold medal. In recognition of his performances, Durant was named the 2016 co-USA Basketball Male Athlete of the Year, along with Carmelo Anthony, for the second time in his career.

To begin the 2015–16 season, Durant and Russell Westbrook both dropped 40 points against the Orlando Magic on October 30, becoming the first teammates in NBA history to do so multiple times, having previously done it in 2012. In December against Denver, they became the first teammates to each have at least 25 points and 10 assists in a regulation game since 1996. On April 11, Durant scored 34 points against the Lakers, setting an NBA record for consecutive games scoring 20 or more points with 64. For the year, Durant averaged 28.2 points, 8.2 rebounds, 5 assists, and 1.2 blocks per game, leading the Thunder to 55 wins and the third seed in the West. In Game 2 of the first round of the playoffs against the Mavericks, he scored 21 points but made just 7-of-33 shots in the worst postseason shooting performance, both by percentage and number of misses, of his career. After defeating Dallas, Oklahoma City moved on to face the Spurs in the second round, falling behind 2–1 to start the series. In Game 4, Durant tied his playoff career high with 41 points in a Thunder win. Oklahoma City eventually defeated the Spurs in six games, drawing a matchup with the record-setting 73-win Golden State Warriors in the Conference Finals. Despite going up 3–1, the Thunder were ousted in seven games, with Durant providing 27 points in Game 7.

In 2017, Durant became involved with YouTube. In February, he visited YouTube's headquarters for a speaking engagement. On April 7, 2017, he created a YouTube account and soon began to upload live stream vlogs onto it. In his first vlog, he detailed, "I'm so excited because I got off social media. I got off the Instagram, Twitter, all that stuff, just to distance myself a bit. But somebody talked me into getting on the YouTube." As of January 2018, Durant's YouTube channel has received over 590,000 subscribers and 18 million video views.

On February 13, 2018, Deadline reported that Durant in partnership with Producer Brian Grazer's Imagine Television will create a basketball-themed scripted drama for Apple.