William Collier Sr., nascut William Morenus (Nova York, 12 de novembre de 1864 - Beverly Hills, Califòrnia, 13 de gener de 1944), va ser un escriptor, director i actor nord-americà. Collier va fugir de casa quan només tenia 11 anys per unir-se a una companyia de gira dirigida per Eddie Foy i el 1879 va aparèixer com a menor a H.M.S. Pinafora.

William Collier Sr. was born on November 12, 1864 in New York City, New York, as William Morenus. He was an actor and writer, known for Wife and Auto Trouble (1916), Harmony at Home (1930) and Up the River (1930). He was married to Paula Marr and Louise Allen. He died on January 13, 1944 in Beverly Hills, Los Angeles, California, from pneumonia.