William Molyneux, 4th Earl of Sefton

William Philip Molyneux, 4th Earl of Sefton, KG (14 October 1835 – 27 June 1897) was a British peer.

In 1854, Molyneux became an ensign in the Grenadier Guards and inherited his father's earldom the following year.

He was promoted to captain in 1857, retiring a year later, when he was appointed Lord Lieutenant of Lancashire.

In 1886, he built Abbeystead House in the forest of Wyresdale, Lancashire as a 'private shooting lodge on a grand scale'.

On his death in 1897, his titles passed to his eldest son, Charles.