John Fenwick (died 2 July 1644) was a member of Long Parliament who was disabled from sitting in Parliament on 22 January 1644 because he was a colonel in the Royalist army during the English Civil War.
Fenwick was the son of Sir John Fenwick, 1st Baronet of Wallington Hall, Northumberland. He matriculated from Trinity College, Cambridge at Easter 1628. He was admitted at Gray's Inn on 28 April 1630.
In November 1640, Fenwick was elected Member of Parliament for Morpeth, Northumberland in the Long Parliament. He was colonel of a Cavalier regiment of dragoons, and as a result of opposing the Roundheads, he was disabled from sitting in Parliament on 22 January 1644.
Fenwick was colonel of a regiment of dragoons. He was at the siege of Newcastle, and the skirmish at Corbridge in 1644. He was killed at the Battle of Marston Moor on 2 July 1644.
Fenwick married Mary, daughter of Sir George Selby, of Whitehouse, County Durham.