William Spencer, 2nd Baron Spencer of Wormleighton (christened 4 January 1591 – 19 December 1636) was an English nobleman, politician, and peer from the Spencer family.
Spencer was the son of Robert Spencer, 1st Baron Spencer of Wormleighton, and his wife, Margaret Willoughby, and was baptised on 4 January 1591 at Brington, Northamptonshire. He attended Magdalen College, Oxford, and became a Member of Parliament for Brackley in 1614, for Northamptonshire (1620–22 & 1624–27). From 6 May 1618 to 1621, Spencer held the office of Deputy Lieutenant of Northamptonshire. On 25 October 1627, he succeeded to the title of 2nd Baron Spencer of Wormleighton.
Lord Spencer married Lady Penelope Wriothesley, daughter of Henry Wriothesley, 3rd Earl of Southampton, in 1615, by whom he had three sons and three daughters. He died in December 1636, aged 45, and was succeeded by his eldest son, Henry, who was created Earl of Sunderland in 1643. Lord Spencer's second son the Honourable Robert was created Viscount Teviot in 1685. His daughter Margaret was the third wife of the prominent statesman, Anthony Ashley Cooper, 1st Earl of Shaftesbury.