William Greet (1851 – 25 April 1914) was a British theatre manager from the end of the 19th century and into the 20th century. Originally a business manager for other theatre licensees in the 1880s, he branched out as an independent manager in the 1890s and was associated with various London theatres, principally the Lyric, the Savoy and the Adelphi Theatres.
Greet was the seventh child and eldest son of Captain Wiliam Greet R.N., commander of the recruiting ship H.M.S. Crocodile, and the former Sarah Vallance Barling. Greet's younger brother was the actor-manager Ben Greet. Greet was born on his father's ship, christened at St Peter ad Vincula at the Tower of London, and educated at the Royal Naval School, New Cross. He served as a Lieutenant of the Royal Marine Artillery from 1871 to 1877.
He worked first as a farmer and then began working in theatre management in the 1880s. Between 1884 and 1890, Greet was successively business manager at the Toole's Theatre under its licensee, J. L. Toole, the Novelty Theatre (licensee, Willie Edouin), the Royalty Theatre (licensee, Kate Santley), the Prince of Wales's Theatre (licensee, Horace Sedger), and from 1890 to 1894 the Lyric Theatre, also for Sedger, with whom Greet's wife collaborated on a stage adaptation of the novel The Little Squire.
Greet became a producer and theatre manager in his own right in 1894, as licensee of the Avenue Theatre, starting successfully with the long-running Dandy Dick Whittington by George R. Sims and Ivan Caryll and a popular comedy by F. C. Burnand, Mrs Ponderbury's Past (later billed as Mrs Ponderbury), directed by and starring Charles Hawtrey. In 1896, Greet gave up the licence at the Avenue and moved to the Lyric, where he presented the long-running The Sign of the Cross by Wilson Barrett, also producing an American tour of the play. He followed that success with another, Dandy Dan the Lifeguardsman by Basil Hood and Walter Slaughter, starring Arthur Roberts and W. H. Denny. Greet sat on the Board of Directors of The Lyceum Theatre Ltd. from 1899 until 1902.