John Robert Thompson Jr. (September 2, 1941 – August 30, 2020) was an American professional basketball player and college basketball coach for the Georgetown Hoyas men's team. He became the first African-American head coach to win a major collegiate championship in basketball when he led the Hoyas to the NCAA Division I national championship in 1984. Thompson was inducted into the Naismith Memorial Basketball Hall of Fame and National Collegiate Basketball Hall of Fame.

Thompson played college basketball for the Providence Friars and earned honorable mention All-American honors in 1964. He played for two seasons in the National Basketball Association (NBA) for the Boston Celtics, who won an NBA championship in both seasons. Thompson became a high school coach in Washington, D.C., before coaching Georgetown for 27 seasons. He worked as a radio and television sports commentator after his retirement from coaching. Thompson earned a master's degree in Counseling and Guidance at the University of the District of Columbia (UDC). He also served as an employee at the center for 4-H and Youth Development at UDC.

Thompson was born and raised in Washington, D.C., and was a practicing Roman Catholic. As a child, his mother insisted on sending him to Catholic schools for the educational opportunities and academic challenges.

At Archbishop Carroll High School, Thompson emerged as a standout center, playing in three consecutive City Championship games (1958–60). In 1959, Carroll All-Mets Thompson, Monk Malloy, George Leftwich and Tom Hoover won over Cardozo 79–52. The next year, Thompson and Leftwich led the Lions over the Ollie Johnson/Dave Bing led Spingarn, 69–54. During his senior year, Thompson led Carroll to a 24–0 record, preserving their 48-game winning streak along the way. Carroll capped off the undefeated 1960 season with a 57–55 win over St Catherine's Angels of Racine, Wisconsin in the Knights of Columbus National Championship Tournament with Thompson scoring a team-high 15 points and adding 12 rebounds.

He was voted to the all-tournament team and was later named a second-team Parade All-American.

After graduating from Archbishop Carroll, Thompson went to Providence College, where he played on the 1963 NIT Championship team with Ray Flynn, and was part of the first Providence NCAA tournament team in his senior year in 1964, when he received honorable mention from the Associated Press for its All-American team. Upon graduation, Thompson was the Friars' all-time leader in points, scoring average, and field goal percentage, and second in rebounds to former teammate Jim Hadnot.

He was selected in the third round of the 1964 NBA draft and played two seasons in the National Basketball Association (NBA) for the Boston Celtics from 1964 to 1966. At 6 ft 10 in (2.08 m) and 270 lb (120 kg), he backed up Bill Russell, the Celtics star center, en route to consecutive NBA championships. Nicknamed "the Caddy" for his secondary role to Russell, he averaged 3.5 points and 3.5 rebounds in 74 games played. Thompson was selected by the Chicago Bulls in the 1966 NBA expansion draft, but he decided to retire from playing instead of relocating to Chicago.

Thompson was a guidance counselor and head coach at St. Anthony High School in Washington, D.C. from 1966 to 1972, compiling a 122–28 record. He left St. Anthony for Georgetown University, who chose him over more experienced candidates Morgan Wootten and George Raveling.