| Honorific-Prefix: | The Right Honourable |
| The Viscount De L'Isle | |
| Office1: | Lord Lieutenant of Kent |
| Monarch1: | Elizabeth II |
| Term Start1: | 1 September 2011 |
| Predecessor1: | Allan Willett |
| Term End1: | 21 April 2020 |
| Successor1: | Annabel Campbell, Baroness Colgrain |
| Office2: | Member of the House of Lords |
| Status2: | Lord Temporal |
| Term Label2: | as a hereditary peer |
| Term Start2: | 5 April 1991 |
| Term End2: | 11 November 1999 |
| Predecessor2: | The 1st Viscount De L'Isle |
| Successor2: | Seat abolished |
| Birth Date: | 21 April 1945 |
| Children: | 2 |
| Parents: | William Sidney, 1st Viscount De L'Isle Jacqueline Vereker |
| Alma Mater: | Royal Military Academy Sandhurst |
| Allegiance: | United Kingdom |
| Branch: | British Army |
| Serviceyears: | 1966–1979 |
| Rank: | Major |
| Unit: | Rifle Brigade Grenadier Guards |
| Battles: | The Troubles |
Philip John Algernon Sidney, 2nd Viscount De L'Isle, (born 21 April 1945), is a British 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. After service in the Rifle Brigade, in 1966, he became a major in the Grenadier Guards and took early retirement in 1979, having spent some of his service in Northern Ireland during The Troubles.
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. On 1 September 2011, he was appointed Lord Lieutenant of Kent. He was appointed Commander of the Order of Saint John in 2012, and Commander of the Royal Victorian Order (CVO) in the 2019 Birthday Honours.
On 15 November 1980, De L'Isle married Isobel Tresyllian Compton, youngest daughter of civil servant Sir Edmund Compton. They have two children: Sophia Jacqueline Mary Sidney (born 1983) and Philip William Edmund Sidney (born 1985).
De L'Isle succeeded to his father's titles in 1991. The family seat is Penshurst Place in Kent.