Jahnsson is a surname. Notable people with the surname include:
Jean Jahnsson (1854–1944), Swedish jeweller, art collector and Consul General Kai Jahnsson (born 1965), Finnish sport shooter who competes in the men's 10 metre air pistol Sirkka Jahnsson or Sirkka Sari (1920–1939), Finnish actress Yrjö Jahnsson (1877–1936), Finnish economics professor at the University of Helsinki
See also Yrjö Jahnsson Award Yrjö Jahnsson Foundation Janson Jansson