| Dermot O'Brien | |
| Fullname: | Dermot Patrick John O'Brien |
| Birth Date: | 28 April 1906 |
| Birth Place: | Mitiamo, Victoria |
| Death Place: | Sydney |
| Originalteam: | Old Xaverians |
| Statsend: | 1928 |
| Years1: | 1926–1927 |
| Games Goals1: | 15 (0) |
| Years2: | 1928 |
| Games Goals2: | 5 (0) |
| Games Goalstotal: | 20 (0) |
Dermot Patrick John O'Brien (28 April 1906 – 7 February 1988) was an Australian rules footballer who played with St Kilda and Hawthorn in the Victorian Football League (VFL).