| State1: | Alabama |
| District1: | 3rd |
| Term Start1: | June 29, 1914 |
| Term End1: | March 3, 1915 |
| Predecessor1: | Henry D. Clayton |
| Successor1: | Henry B. Steagall |
| Office2: | Member of the Alabama House of Representatives |
| Term2: | 1911 |
| Birth Name: | William Oscar Mulkey |
| Birth Date: | 27 July 1871 |
| Birth Place: | Brundidge, Alabama |
| Death Place: | Geneva, Alabama |
| Party: | Democratic |
William Oscar Mulkey (July 27, 1871 – June 30, 1943) was a U.S. Representative from Alabama.
Born in Brundidge, Alabama, Mulkey attended the public schools and graduated from State Normal College, Troy, Alabama, (now Troy University) in 1892.He studied law.He was admitted to the bar in 1893 and commenced practice in Troy, Alabama, in 1894.He served as member of the State constitutional convention in 1901.He served in the State house of representatives in 1911.
Mulkey was elected as a Democrat to the Sixty-third Congress to fill the vacancy caused by the resignation of Henry D. Clayton and served from June 29, 1914, to March 3, 1915.He was not a candidate for renomination in 1914.He resumed the practice of law.He died in Geneva, Alabama, June 30, 1943.He was interred in Geneva Cemetery.