| Kaj Frederiksen | |
| Birth Place: | Gørlev, Denmark |
| Birth Date: | 21 September 1916 |
| Death Place: | Copenhagen, Denmark |
| Occupation: | boxer |
| Relatives: | Viggo Frederiksen (twin brother) |
Kaj Frederiksen (21 September 1916 – 9 July 1991) was a Danish boxer who competed in the 1936 Summer Olympics.
He was born in Gørlev and died in Copenhagen. He was the twin brother of Viggo Frederiksen.
In 1936 he was eliminated in the second round of the flyweight class after losing his fight to the upcoming silver medalist Gavino Matta.