William Joseph Mosconi (; June 27, 1913 – September 17, 1993) was an American professional pool player from Philadelphia, Pennsylvania. Between the years of 1941 and 1957, he won the World Straight Pool Championship nineteen times. For most of the 20th century, his name was essentially synonymous with pool in North America – he was nicknamed "Mr. Pocket Billiards" – and he was among the first Billiard Congress of America Hall of Fame inductees. Mosconi pioneered and regularly employed numerous trick shots, set many records, and helped to popularize pool as a national recreation activity.

During the 1940s and 1950s, the pocket billiards game most often played in competition was called straight pool, or 14.1 continuous, a form of pool considered by most top players to be more difficult than today's fast tournament game nine-ball. Mosconi set the officially-recognized straight pool high run world record of 526 consecutive balls in 1954.