Sven Oscar Kullander (born in Sollefteå, 1952) is a Swedish biologist specialised in ichthyology. He primarily researches cichlids – notably the genus Apistogramma and the Cichlasoma-complex – and other tropical fresh water fishes. He also has been working with endangered fish species in Sweden.
He studied at the universities of Umeå and Stockholm, and took his Ph.D. in Stockholm in 1984. He is currently senior curator at the Swedish Museum of Natural History in Stockholm, with the responsibility for the ichthyologic and herpetologic collections. Kullander also coordinates the museum's contributions to FishBase.
Kullander has produced more than 100 scientific and popular publications on fishes, and described many groups and new species of cichlids.
The Swedish aquarists' magazine Tidskriften Akvariet gave him "Akvariets Oscar" ("the Aquarium Academy Award") in 1996 for his great contribution to the aquarium hobby. His wife Fang Fang Kullander (1962–2010) was also an ichthyologist at the Swedish Museum.