William Samuel Lilly (10 July 1840 – 29 August 1919)[1] was an English barrister and man of letters.

After some private tuition from Sir Adolphus William Ward, he entered the Indian civil service, becoming in 1869 secretary to the government of Madras.

Owing to a breakdown in health, however, he had to return to England, where he devoted himself to a career in literature.

With his wide-ranging intellectual interests, Lilly occasionally wrote for some of the major publications of his time, such as The Nineteenth Century, The Contemporary Review, The Fortnightly Review, Popular Science Monthly, and The Dublin Review.

Lilly was a convert to Roman Catholicism, and from 1874 was secretary to the Catholic Union of Great Britain.