Muriel Beaumont, Lady du Maurier (1881 – 27 November 1957) was an English stage actress. She was the wife of the actor Gerald du Maurier and mother of the writer Daphne du Maurier. She retired from the stage in 1910.
Beaumont was the daughter of Harry Beaumont, a solicitor. Despite his disapproval, she became an actress. Her first appearance was at the Haymarket Theatre in 1898. In 1902 she was cast as Lady Agatha in The Admirable Crichton. Also in the cast was Gerald du Maurier, whom she had met only once before. Within five months they were married.
After marriage, Beaumont maintained her stage career until 1910 before retiring. In 1905 she played Nerissa to Violet Vanbrugh's Portia in The Merchant of Venice. She also appeared in English translations of light French comedies. In 1908 she appeared with Weedon Grossmith and A. E. Matthews in Frederick Lonsdale's farce The Early Worm. She and her husband never appeared on stage together after The Admirable Crichton.
The couple had three children: Angela du Maurier (1904–2002); Daphne du Maurier (1907–1989); and Jeanne du Maurier (1911–1996/97). Beaumont died at her home in Cornwall aged 76.