Sir John Lowther, 1st Baronet (20 February 1605 – 30 November 1675) was an English lawyer, landowner, and politician who sat in the House of Commons for Westmorland in 1628 and in 1660.
He stood for election to both Parliaments of 1640, but was defeated on each occasion by Sir Philip Musgrave.
He was recommended to continue as a justice of the peace for Westmorland (having sat on the bench since 1641) and was fined on relatively favourable terms.
Moderately active during the Parliament, his one recorded speech was to oppose Charles Howard's bill for curbing the moss troopers, preferring older methods of keeping peace on the border.
The writer Alice Thornton, a sister of his son-in-law Christopher Wandesford, accused him of persuading her brother to attempt to cheat her and their mother out of the legacies due to them under the will of her father, the Lord Deputy of Ireland, thereby causing a long and bitter family lawsuit.