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 took no great part in the English Civil Wars.
Lowther was the eldest son of Sir John Lowther of Lowther Hall and his wife Eleanor Fleming, daughter of Wiliam Fleming of Rydal. He attended the Inner Temple in 1621 and was called to the bar in 1630.
In 1628, Lowther was elected Member of Parliament for Westmorland, together with his father and sat until 1629 when King Charles decided to rule without parliament for eleven years. In 1636, he became recorder of Kendal. He was created a baronet in the Baronetage of Nova Scotia in around 1638. He stood for election to both Parliaments of 1640, but was defeated on each occasion by Sir Philip Musgrave.
Lowther was a commissioner of array for Cumberland and Westmorland in 1642. He was commissioned a colonel by the Royalists during the Civil War and was Governor of Brougham Castle until 1644. However, he claimed not to have borne arms against the Parliamentarians, and took the Covenant when their forces approached. 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. He did not continue as a justice or in the recordership of Kendal after 1648, during the Interregnum.