John Mostyn (died 1644) was a Welsh politician who sat in the House of Commons at various times between 1625 and 1640.
In April 1640, Mostyn was elected MP for Flintshire in the Short Parliament.
He was re-elected MP for Flintshire for the Long Parliament in November 1640.
[2] He was disabled from sitting in parliament for supporting the King on 5 February 1644.
[1] Mostyn died unmarried at his seat at Maesmynau in 1644.