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