| Country: | Sweden |
| Birth Date: | 16 March 1892 |
| Birth Place: | Gothenburg, Sweden |
| Death Place: | Gothenburg, Sweden |
Karl Mathias Berndtsson Kullberg (16 March 1892 – 29 September 1943) was a Swedish chess master who was born and died in Göteborg.
He won at Copenhagen 1916,[1] and lost a match for the Swedish Chess Championship to Gustaf Nyholm (1½–3½) in 1917. He was first in the national tournaments in 1918, 1920, 1921 (jointly), and 1926. He took 14th at Göteborg 1920 (Paul Johner won),[2] won Nordic Chess Championship at Oslo 1928,[3] and took 6th at Örebro 1935 (Alexander Alekhine won).[4]
Berndtsson played for Sweden in three Chess Olympiads:
and won team bronze medal in 1933.[5]