Dorothy Sidney, Countess of Leicester (née Percy; c.1598 – August 20, 1659) was the eldest daughter of Henry Percy, 9th Earl of Northumberland and the former Lady Dorothy Devereux.

In 1615, she married Robert Sidney, 2nd Earl of Leicester. The couple had several children, including:

• Dorothy (1617-1683), married Henry Spencer, 1st Earl of Sunderland.
• Philip (1619-1697), the 3rd Earl, married Lady Catherine Cecil.
• Henry, Earl of Romney, died unmarried and without issue.
• Algernon, died unmarried and without issue.
• Robert, died young.
• Lucy (d. 1685), married Sir John Pelham.