| Alf Martinsen | |
| Birth Date: | 29 December 1911 |
| Birth Place: | Lillestrøm, Norway |
| Death Place: | Lillestrøm, Norway |
| Position: | Striker |
| Clubs1: | Lillestrøm Fram |
| Clubs2: | Lillestrøm SK |
| Nationalyears1: | 1936–1946 |
| Nationalteam1: | Norway[1] |
| Nationalcaps1: | 25 |
| Nationalgoals1: | 10 |
| Manageryears1: | 1947–1950 |
| Manageryears2: | 1952–1953 |
| Managerclubs2: | Lillestrøm SK |
Alf "Kaka" Martinsen (29 December 1911 – 23 August 1988) was a Norwegian football player. At the 1936 Summer Olympics he was a member of the Norwegian team which won the bronze medal in the football tournament.[2] He also took part in the 1938 FIFA World Cup, but did not play a single match. On club level he started his career in Lillestrøm-based workers' team Fram, before joining Lillestrøm SK.
He coached Lillestrøm SK from 1947 to 1950 and from 1952 to 1953.[3]