Clarence Alfred Barnes (August 28, 1882[1] – May 26, 1970[2]) was an American politician who served as attorney general of Massachusetts from 1945 to 1949.

[3][4] His oldest son Clare Barnes Jr. was an advertising executive who published a best-selling series of picture books.

From 1912 to 1913, he served as a state representative, and he was a delegate to the Massachusetts Constitutional Convention of 1917–18.

[1] Barnes was the Republican nominee for attorney general in 1938 but lost to incumbent Paul A.

[3] Barnes died on May 26, 1970, at Martha's Vineyard Hospital in Oak Bluffs, Massachusetts.