Lilian Baylis (May 9, 1874 - November 25, 1937) was a British theatrical producer and manager and the founder of a ballet company.

Born in London, England, in 1898 she assisted her aunt, Emma Cons in running The Royal Victoria Hall And Coffee Tavern near Waterloo in London. Following Cons' death in 1912, she took over the management of the theatre, renamed it the "Old Vic" and ran it for the rest of her life. One of her finest achievements at the Old Vic was to produce a full cycle of Shakespeare's plays, starting with The Taming of the Shrew in 1914 to Troilus and Cressida in 1923.

In 1925, Baylis sought to re-open the derelict Sadler's Wells Theatre and in 1927 established a ballet company there. For the first few years the drama and ballet companies, known as the "Vic-Wells" companies, rotated between the two theatres, with the ballet becoming permanently based at Sadler's Wells in 1935.

In 1928 the ballet company engaged Ninette de Valois, under whose direction British classical ballet developed at Sadler's Wells until eventually the ballet company became known as the Sadler's Wells Royal Ballet Company until it moved to Birmingham in 1990.

The current Sadler's Wells theatre contains a 200-seat theatre named in her honour.