| William St. John Forman | |
| Office1: | 14th Commissioner of Internal Revenue |
| President1: | Grover Cleveland William McKinley |
| Term Start1: | November 27, 1896 |
| Term End1: | December 31, 1897 |
| Predecessor1: | Joseph S. Miller |
| Successor1: | Nathan B. Scott |
| State2: | Illinois |
| Term Start2: | March 4, 1889 |
| Term End2: | March 3, 1895 |
| Predecessor2: | Jehu Baker |
| Successor2: | Frederick Remann |
| Office3: | Member of the Illinois Senate |
| Term3: | 1884-1888 |
| Birth Date: | 20 January 1847 |
| Birth Place: | Natchez, Mississippi |
| Death Place: | Champaign, Illinois |
| Party: | Democratic |
William St. John Forman (January 20, 1847 - June 10, 1908) was a U.S. Representative from Illinois.
Born in Natchez, Mississippi, Forman moved with his father to Nashville, Washington County, Illinois, in 1851. He attended the public schools, and Washington Seminary, Richview, Illinois. He studied law, was admitted to the bar in 1870, and commenced practice in Nashville, Illinois.
He served as mayor of Nashville, Illinois from 1878 to 1884, and was a delegate to all State and National Democratic Conventions from 1876 to 1896. He was a member of the Illinois Senate from 1884 to 1888. Forman was elected as a Democrat to the Fifty-first, Fifty-second, and Fifty-third Congresses (March 4, 1889 - March 3, 1895). He served as chairman of the Committee on Militia during the Fifty-third Congress.
Forman moved to East St. Louis, Illinois in 1895, where he resumed practicing law. He was an unsuccessful candidate as a Gold Standard Democrat for election as governor in 1896. He was appointed by President Grover Cleveland as Commissioner of Internal Revenue and served from 1896 to 1897. Forman died in Champaign, Illinois on June 10, 1908. He was interred in Masonic Cemetery, Nashville, Illinois.