| Tommy O'Day | |
| Fullname: | Thomas O'Day |
| Birth Date: | 8 October 1873 |
| Birth Place: | North Melbourne, Victoria |
| Death Place: | Hotham West, Victoria |
| Originalteam: | Imperials |
| Debutdate: | Round 1, 1898 |
| Debutteam: | Carlton |
| Debutopponent: | South Melbourne |
| Debutstadium: | Princes Park |
| Years1: | 1898 |
| Club1: | Carlton |
| Games Goals1: | 13 (8) |
Thomas O'Day[1] (8 October 1873 – 2 September 1905) was an Australian rules footballer who played for North Melbourne in the Victorian Football Association (VFA). He then played for the Imperials (a forerunner of) in the West Australian Football Association (WAFA), and then for in the Victorian Football League (VFL).[2]
O'Day made his debut for the Carlton Football Club in Round 1 of the 1898 season. He was only with Carlton for the single season, playing 13 games and kicking 8 goals. The 8 goals he kicked made him the club's leading goal-kicker for that year -- the lowest leading goal tally in the club's history.