Carl William Demarest (February 27, 1892 – December 28, 1983) was an American actor, known especially for his supporting roles in screwball comedies by Preston Sturges and as Uncle Charley in the sitcom My Three Sons from 1965-72.

Among these he had prominent roles in The Lady Eve, Sullivan's Travels, Hail the Conquering Hero, and The Miracle of Morgan's Creek.

Demarest was such a familiar figure at the Paramount studio that just his name was used in the movie Sunset Boulevard as a potential star for William Holden's unsold baseball screenplay.

He played folksy Jeb Gaine, an occasional sidekick to the main character, in the 1961–62 season of the Western series Tales of Wells Fargo.

Demarest had worked with Fred MacMurray previously in the films Hands Across the Table (1935), Pardon My Past (1945), On Our Merry Way (1948), and The Far Horizons (1955) and was a personal friend.

[12] Thayer, who later became an activist on health issues in the motion picture industry, was appointed California's lay-chairman of the American Nurses Association in October 1960.