William Fitzwilliam, 2nd Baron Fitzwilliam MP (c.1609 – 21 February 1658) was an English nobleman and politician who sat in the House of Commons of England between 1640 and 1653.

He was re-elected in November 1640 for the Long Parliament where he remained throughout its duration.

On 11 Jul 1638 Fitzwilliam married Jane Hunter Perry (1611-8 Apr 1671), daughter of Hugh Perry and his wife Catherine Fenn.

Their son William succeeded to the title and was later created Earl Fitzwilliam.

Their daughter Jane FitzWilliam (1646-1679) married Sir Christopher Wren.