Philip John Algernon Sidney, 2nd Viscount De L'Isle (born 21 April 1945), is a British hereditary peer and former soldier.

Lord De L'Isle is the only son of William Sidney, 1st Viscount De L'Isle, and his wife Jacqueline (née Vereker), a daughter of Field Marshal John Vereker, 6th Viscount Gort.

He was educated at Tabley House, Mons Officer Cadet School and the Royal Military Academy Sandhurst.

De L'Isle was appointed Vice-Lieutenant of Kent in 2002 and is also a Freeman of the City of London and a member of the Worshipful Company of Goldsmiths.

Viscount De L'Isle is a descendant of King William IV though his illegitimate daughter Lady Sophia FitzClarence.