William Mann was an English politician who sat in the House of Commons from 1621 to 1625.
He was a vestryman of St Margaret's, Westminster.
Following the death of Edmund Doubleday in 1620, shortly after he was elected Member of Parliament for Westminster, the then dean of Westminster John Williams was the prime mover in arranging the by-election.
In this, Williams promoted Mann as his candidate.
He was re-elected MP for Westminster in 1624 and 1625.