John Sidney, 6th Earl of Leicester (February 14, 1680 - September 27, 1737), was a Privy Councillor during the Georgian era.

He was born and died at his family home of Penshurst Place in Kent and is buried at Penshurst. He was one of the five sons of Robert Sidney, 4th Earl of Leicester . (1649-1702) by Lady Elizabeth Egerton (1653-1709), the daughter of John Egerton, 2nd Earl of Bridgewater.

John inherited the earldom from his brother, Philip Sidney, 5th Earl of Leicester , in 1705. Their younger brother Jocelyn Sidney followed as 7th Earl of Leicester.

|- style="text-align: center;" | width="30%" |Preceded by:
Lord Stanhope | width="40%" style="text-align: center;" |Captain of the Yeomen of the Guard
1725–1731 | width="30%" |Succeeded by:
The Earl of Ashburnham