| William R. Callahan | |
| State House1: | Massachusetts |
| District1: | 16th Middlesex |
| Term Start1: | January 6, 1971 |
| Term End1: | January 3, 1973 |
| Predecessor1: | Edward M. Flanagan |
| Successor1: | Ed Markey |
| Birth Date: | April 27, 1925 |
| Birth Place: | Malden, Massachusetts |
| Death Date: | January 1976 |
| Death Place: | Malden, Massachusetts |
| Nationality: | American |
| Party: | Democratic |
William R. Callahan (April 27, 1925 – January 1976) was a Democratic member of the Massachusetts House of Representatives. He was a Malden resident who represented the 16th Middlesex district for one term, from 1971 to 1973. Before serving in the state legislature, he was a member of the Malden Common Council for two years and the Malden City Council for 14 years. He was a member of multiple organizations, including the Knights of Columbus and the Ancient Order of Hibernians.[1]