| Austin Belknap | |
| Term Start: | January 3, 1876 |
| Term End: | January, 1878 |
| Office2: | Chairman of the Somerville Massachusetts Board of Selectmen |
| Term Start2: | 1870 |
| Term End2: | January 2, 1872 |
| Predecessor2: | Frances Houghton |
| Successor2: | George O. Brastow, Mayoralty; Selectmen's Office Abolished |
| Office3: | Member of the Somerville Massachusetts Board of Selectmen |
| Term Start3: | 1869 |
| Term End3: | January 2, 1872 |
| Predecessor3: | New position Board of Selectmen expanded from five to nine members. |
| Successor3: | George O. Brastow, Mayoralty; Selectmen's office abolished |
| Office4: | Member of the Somerville Massachusetts School Committee |
| Term Start4: | 1862 |
| Term End4: | 1864 |
| Birth Date: | July 18, 1819 |
| Death Date: | December 9, 1902 |
| Nationality: | American |
| Spouse: | Jane P. Brigham |
| Children: | Robert W. Belknap |
| Alma Mater: | Worcester Manual Labor High School |
| Profession: | Civil engineer, engaged in Railway construction until 1843; Produce business from 1843 to December 1902 |
Austin Belknap (July 18, 1819 – December 9, 1902) was a Massachusetts businessman and politician who served as a member, and last Chairman, of the Board of Selectmen of Somerville, Massachusetts, and as the third Mayor, of Somerville.
Belknap was born July 18, 1819, in Westboro, Massachusetts, to John and Ruth (Fay) Belknap of Westboro.