| Office: | Teachta Dála |
| Term Start: | July 1937 |
| Term End: | 12 March 1951 |
| Constituency: | Galway West |
| Term Start1: | September 1927 |
| Term End1: | January 1933 |
| Constituency1: | Galway |
| Birth Date: | 4 March 1880 |
| Birth Place: | County Galway, Ireland |
| Death Place: | County Galway, Ireland |
Joseph William Mongan (4 March 1880 – 12 March 1951) was an Irish politician. He was an unsuccessful candidate at the June 1927 general election, but was elected to Dáil Éireann as a Cumann na nGaedheal Teachta Dála (TD) for the Galway constituency at the September 1927 general election.[1] He was re-elected at the 1932 general election but lost his seat at the 1933 general election.[2]
At the 1937 general election, he was elected as a Fine Gael TD for the Galway West constituency. He was re-elected at each subsequent general election and served until his death in 1951. No by-election was held for his seat.