John William "Jack" McCloskey (born October 19, 1925) is a retired American basketball player, coach and executive. He served in World War II as a lieutenant commanding a landing ship for Marines. He played one game for the Philadelphia Warriors of the NBA during the 1953 season, scoring 6 points in that game. Two decades later, he served as the head coach of the Portland Trail Blazers from 1972 through 1974, earning a 48-116 win/loss record. He followed this stint as an assistant coach to Jerry West and the Los Angeles Lakers. When West became general manager, McCloskey felt he had earned the right to become head coach, but Paul Westhead was hired instead. In 1979, he became general manager of the Detroit Pistons.
During the next 13 years, "Trader Jack," as he was known, made over 30 trades, constantly upgrading his team to become a true challenger to the Boston Celtics, one of the dominant teams in the NBA's Eastern Conference. His best-known moves were drafting Joe Dumars and Dennis Rodman in the lower rounds of the NBA Draft, trading three players for future all-star center and dominant rebounder Bill Laimbeer and trading superstar Adrian Dantley for Mark Aguirre during the 1988-89 season, a move that helped the Pistons win the NBA championship in 1989 and 1990. After the Chicago Bulls swept an injury-riddled Piston team in the 1991 Eastern Conference Finals, "Trader Jack" made his last moves. He acquired Darrell Walker, Brad Sellers, and Orlando Woolridge, and let go of Vinnie Johnson and James Edwards to try and make the team younger. He drafted Doug Overton in the second round that year (the Pistons had traded their first-round pick away), who did not even play the following season. The Pistons struggled with their chemistry, as key subs like John Salley did not improve their performance, yet they won 48 games. They lost in five games to the New York Knicks in the first round, and McCloskey left the team. He later served in the front offices of the Minnesota Timberwolves, and the Toronto Raptors, the latter on an interim basis.
On March 29, 2008, McCloskey had his name honored in Detroit, with banner raised at The Palace of Auburn Hills.
His daughter is the writer Molly McCloskey, whose memoir Circles Around the Sun: In Search of a Lost Brother (2011) recounts the story of the McCloskey family with particular focus on Molly's brother (Jack McCloskey's son), Mike.