Košarkaški klub Partizan (Serbian Cyrillic: Кошаркашки клуб Партизан, lit. 'Basketball Club Partizan'), commonly known as Partizan Belgrade, or as Partizan Mozzart Bet for sponsorship reasons, is a professional basketball club based in Belgrade, Serbia. It is part of the multi-sports Belgrade-based club Partizan. The club is a founding member and shareholder of the Adriatic Basketball Association, and competes in the Serbian League (KLS), the ABA League, and the continental top-tier EuroLeague.

Since 1945, Partizan has won 51 trophies and is the holder of the 22 national champion titles. They have also won 16 national basketball cups, 8 ABA League championships and 1 ABA League Supercup, and most notably the European Champion trophy at the Final Four of the EuroLeague in Istanbul in 1992. The final game was notable for the buzzer-beater by Aleksandar Đorđević which ranks among the most famous shots in basketball history. They also won 3 Korać Cups in 1978, 1979 and 1989 and participated in four Euroleague Final Fours. In September 2009, Partizan became the first and to this day the only Serbian team to play an official game against an NBA team.

The club was established on 4 October 1945, as a basketball section of the Sports Association of the Central House of the Yugoslav Army. The first club championship of Yugoslavia was held in 1946, and Partizan participated with a team consisting mostly of players from Yugoslav Army basketball team, which in 1945 won the unofficial state championship against the teams of Yugoslav republics. KK Partizan officially split from the Army in 1953, since the entire sports society became independent and was renamed as Partizan Yugoslav Sports Association (JSD Partizan).

Although with a strong roster, including many players who played for the national team of Yugoslavia, Partizan waited for the first title of Yugoslav champion until 1976. In the first 30 years of its history, most well-known Partizan players have included Mirko Marjanović, Božidar Munćan, Radomir Šaper, Vilmoš Loci, Lajoš Engler, Čedomir Stojičević, Borislav Stanković, Borislav Ćurčić, Branko Radović, Radovan Radović, Miloš Bojović, Dragutin Čermak, Slobodan Jelić and others. During this period Partizan finished second-placed in the championship of Yugoslavia on five occasions. On two occasions (in 1950 and 1951) it even had the same number of points as the winner, but barely missed the title of national champion.

The rise of Partizan into a major basketball club that will eventually become one of the most successful in Europe, started in the early 70's, when former players took over the management and the coaching job was taken by national team coach Ranko Žeravica. He selected a group of young players led by exceptionally talented Dražen Dalipagić and Dragan Kićanović. Since Žeravica, as the national team coach (until 1965 as an assistant to Aleksandar Nikolić and then as head coach), closely followed the trends of international basketball for more than ten years, including the NBA, he aimed to combine the best features of American and Soviet concepts of the game, and adapt them to the specifics and the mentality of the players from Belgrade, Serbia and the rest of Yugoslavia. He gathered around him other young coaches, and in the late 1970s, when Žeravica went coaching abroad, his former associates Borislav Ćorković and Dušan Ivković successfully took over the team.

This important period in the club's history was crowned with several trophies. The first of these was the title of Yugoslav champion in 1975–76 season. Partizan also started to make noise in the European competitions with two back-to-back titles in the European Korać Cup (1978 in Banja Luka, KK Bosna was defeated with 117–110, while in 1979 Partizan defeated Italian Arrigoni 108–98). The first double was won in 1978–79 and another national championship title came in 1980–81.

In addition to coaches Žeravica, Ćorković and Ivković, notable players included, above all Dražen Dalipagić and Dragan Kićanović, but also Dragutin Čermak, Goran Latifić (captain of the first championship team in 1976), Josip Farčić, Dragan Todorić, Dušan Kerkez, Miodrag Marić, Boban Petrović, Arsenije Pešić, Boris Beravs, Milenko Savović, Jadran Vujačić, Nebojša Zorkić, Žarko Zečević and others.

After a couple of quiet years and a generational shift, a new generation of top players developed towards the end of the 1980s, under the leadership of the new club director, Dragan Kićanović.