| Birth Date: | 19 May 1986 |
| Birth Place: | Iceland |
| Sport: | Athletics |
| Event: | Marathon |
Kári Steinn Karlsson (born 19 May 1986) is an Icelandic long-distance runner. At the 2012 Summer Olympics, he competed in the men's marathon, finishing in 42nd place.
Kári went to University of California, Berkeley.