Clas is a masculine given name. Notable people with the name include:
Clas Alströmer (1736–1794), Swedish naturalist
Clas Bjerkander (1735–1795), Swedish meteorologist, botanist and entomologist
Clas or Klaus Fleming (1535-1597), Finnish-born Swedish nobleman and admiral, Lord High Admiral and Lord High Constable
Clas Fleming (admiral) (1592-1644), an admiral and administrator of the Royal Swedish Navy
Clas Frietzcky (1727–1803), Swedish politician
Clas Lindberg (born 1956), Swedish film director and screenwriter
Clas Theodor Odhner (1836-1904), Swedish historian and director of the Swedish National Archives
Clas Thunberg (1893-1973), Finnish speed skater and five time Olympic gold medalist
Clas Åkesson Tott (c. 1530–1590), Swedish field marshal and member of the Privy Council of Sweden
