Björn Ahlgrensson was a Swedish painter.

Björn Ahlgrensson, the son of a decorative painter, spent his childhood in Copenhagen and Paris, where he also went to school. He learned decorative painting from Karl Grabow in Stockholm, where he studied from 1891 to 1893 at the school of the Swedish Konstnärsförbundet. In 1893 he received a scholarship that he used for a study trip to Paris, but he had to break off his study trip due to lack of money.

In 1899 he married Elsa, the sister of his painter friend Fritz Lindström, and the family moved together to Värmland, where he joined the Rackengruppen artists colony. But he was denied public success and life was marked by poverty and isolation. His art took on a melancholic undertone, such as B. in Skymmningsglöden (1903).

In 1917, however, he left Arvika and his marriage and went to Stockholm, where he made new contacts, and to Jämtland . But the following year he fell ill with the Spanish flu and died.