William A. Sharsig (1855 – February 1, 1902) was an American Major League Baseball co-owner, general manager, business manager^[1] and on field manager of the American Association Philadelphia Athletics, both their first incarnation and their second, which had migrated over from the Players' League. He lived, worked, and was born in Philadelphia.^[2]

Sharsig founded the Athletics in September 1880. In 1881, the team went on a barnstorming tour, and Sharsig took on two partners: player Charlie Mason and manager Horace Phillips.^[3] After the tour, Phillips jumped ship to the Philadelphia Quakers, a competing team founded by Al Reach, which eventually became the Philadelphia Phillies, and was replaced on the management team by minstrel show performer Lew Simmons.^[3]

As co-owner of the team, Bill named himself manager of his team on several occasions.^[4] In five seasons; 1886, and from 1888 to 1891. He finished his career with 238 wins and 216 losses for a .524 winning percentage.^[2]

After the Association folded in 1891, Bill went on to manage the Indianapolis team in the Western League in 1892 and in 1894.^[5] Bill died in his hometown of Philadelphia, and was interred at Mount Vernon Cemetery.^[2]