Nance O'Neil, born Gertrude Lamson, was an American stage and screen actress. When she decided to become an actress, her religious father, George Lamson, an auctioneer, denounced his daughter in church for going on the stage and asked the congregation to pray for her. O'Neil's first performance in a professional production was in the role of a nun in Sarah at the Alcazar Theatre in San Francisco on October 16, 1893. At the height of her career, she was promoted on theatre bills and in period trade publications and newspapers as the "American Sarah Bernhardt".

Gertrude Lamson (Oakland, Califòrnia, 8 d’octubre de 1874 - Englewood, Nova Jersey, 7 de febrer de 1965), coneguda professionalment com Nance O'Neil o Nancy O'Neil, va ser una actriu d'escenari i cinema nord-americà que va actuar en obres de teatre a diversos teatres d'arreu del món, però que va treballar principalment als Estats Units entre els anys 1890 i 1930.