Novak Djokovic (born 22 May 1987) is a Serbian professional tennis player. He has been ranked as the world No. 1 in men's singles by the Association of Tennis Professionals (ATP) for a record 428 weeks, and finished as the year-end No. 1 a record eight times and has been ranked No. 1 at least once in a year for a record 13 different years. Djokovic has won 100 ATP Tour-level singles titles, including a record 24 majors, a record 10 Australian Open titles, a record 40 Masters, a record seven year-end championships, and an Olympic gold medal. Djokovic is the only man in tennis history to be the reigning champion of all four majors at once across three different surfaces. In singles, he is the only man to achieve a triple Career Grand Slam, and the only player to complete a Career Golden Masters, a feat he has accomplished twice. Djokovic is the only player in singles to have won all of the Big Titles over the course of his career.

Djokovic began his professional career in 2003. In 2008, at age 20, he disrupted Roger Federer and Rafael Nadal's streak of 11 consecutive majors by winning his first major title at the Australian Open. By 2010, Djokovic had begun to separate himself from the rest of the field and, as a result, the trio of Federer, Nadal and Djokovic was referred to as the "Big Three" among fans and commentators. In 2011, Djokovic ascended to No. 1 for the first time, winning three majors and a then-record five Masters titles while going 10–1 against Nadal and Federer. He remained the most successful player in men's tennis for the rest of the decade. Djokovic had his most successful season in 2015, reaching a record 15 consecutive finals and winning a record 10 Big Titles while earning a record 31 victories over top 10 players. His dominant run extended through to the 2016 French Open, where he completed his first Career Grand Slam and a non-calendar year Grand Slam, becoming the first man since Rod Laver in 1969 to hold all four majors simultaneously and setting a rankings points record of 16,950.

In 2017, Djokovic suffered from an elbow injury that weakened his results until the 2018 Wimbledon Championships, where he won the title while ranked No. 21 in the world. Djokovic then returned to a dominant status, winning 12 major titles and completing his second and third Career Grand Slams. Due to his opposition to the COVID-19 vaccine, he was forced to skip many tournaments in 2022, notably the Australian Open and the US Open, being deported from the country in the former case. One year after the Australian visa controversy, he made a successful comeback to reclaim the 2023 Australian Open trophy, and shortly after claimed the all-time record for most men's singles majors titles. In 2024, he became the only player to complete a career sweep of the Big Titles.

Representing Serbia, Djokovic led the national tennis team to its first Davis Cup title in 2010, and the inaugural ATP Cup title in 2020. In singles, he won the gold medal at the 2024 Paris Olympics and the bronze medal at the 2008 Beijing Olympics. He is a recipient of the Order of Karađorđe Star, Order of St. Sava, and the Order of the Republika Srpska. He has been named the BTA Best Balkan Athlete of the Year a record eight times.

Beyond competition, Djokovic was elected as the president of the ATP Player Council in 2016. He stepped down in 2020 to front a new player-only tennis association; the Professional Tennis Players Association (PTPA) founded by him and Vasek Pospisil, citing the need for players to have more influence on the tour and advocating better prize money structure for lower ranked players. Djokovic is an active philanthropist. He is the founder of Novak Djokovic Foundation, which is committed to supporting children from disadvantaged communities. Djokovic was appointed a UNICEF Goodwill Ambassador in 2015.

Novak Djokovic was born on 22 May 1987 in Belgrade, SR Serbia, SFR Yugoslavia, to Dijana (née Žagar) and Srdjan Djokovic. He is of paternal Serbian and maternal Croatian descent. His two younger brothers, Marko and Djordje, have also played professional tennis.

Djokovic began playing tennis at the age of four, after his parents gave him a mini-racket and a soft foam ball, which his father said became "the most beloved toy in his life". His parents then sent him to a tennis camp in Novi Sad. In the summer of 1993, as a six-year-old, he was sent to a tennis camp organized by the Teniski Klub Partizan and overseen by Yugoslav tennis player Jelena Genčić at Mount Kopaonik, where Djokovic's parents ran a fast-food parlour. Genčić worked with Djokovic over the following six years, convincing him to hit his backhand with two hands instead of the single hand used by his idol, Pete Sampras. Djokovic has credited Genčić for "shaping my mind as a human being, but also as a professional".

During the Yugoslav Wars in the late 1990s, Serbia had to endure embargoes and NATO bombings because of the Kosovo War. At one point Djokovic had to train inside a disused swimming pool converted into a tennis court. Due to his rapid development, Genčić contacted Nikola Pilić and in September 1999 Djokovic moved to the Pilić tennis academy in Oberschleißheim, Germany, spending four years there. Pilić made him serve against a wall for several months to improve his technique, and he had him working with a rubber exercise band for a year to improve flexibility in his wrist. One of the players he trained with at the Niki Pilić academy was future world No. 10 Ernests Gulbis, with whom he allegedly had a fiery rivalry.