Lewis Watson, 1st Baron Rockingham (1584–1653) was an English landowner and politician who sat in the House of Commons from 1621 to 1624. From 1621 to 1645 when he received his peerage he was known as Sir Lewis Watson, 1st Baronet. He supported the Royalist cause in the English Civil War and as a result was created Baron Rockingham.
Watson was the son of Sir Edward Watson of Rockingham Castle and his wife Anne Digby daughter of Kenelm Digby of Stoke Dry, Rutland. He was baptised at Rockingham on 14 July 1584. He matriculated at Magdalen College, Oxford on 24 May 1590. On 19 August 1608, he was knighted at Grafton. He succeeded to Rockingham Castle, which was leased from the crown, on the death of his father on 4 March 1616 and later acquired the fee of the castle and its lands from the crown .
In 1621, Watson was elected Member of Parliament for Lincoln. He was created a baronet on 23 June 1621. In 1624 he was re-elected MP for Lincoln. He was Sheriff of Northamptonshire from 1632 to 1633. In 1633 he acquired from the Brocas family the title of "hereditary" Master of the Buckhounds which was a serjeanty associated with the Manor of Little Weldon. In 1638 he became verderer of Rockingham and Brigstock.
Watson served the King during the Civil War and as a result was created Baron Rockingham of Northampton on 29 January 1645.
Watson married firstly, in 1609, Catherine Bertie, daughter of Robert Bertie, Lord Willoughby of Eresby and his wife Mary de Vere. She died in childbirth on 15 February 1610, and was buried at Spilsby, Lincolnshire. He married secondly on 3 October 1620, Eleanor Manners, daughter of Sir George Manners, of Haddon Hall, Derbyshire and his wife Grace Pierrepont daughter of Sir Henry Pierrepont. He was succeeded as baron by his son Edward.