Sir Thomas Jermyn (1573–1645) of Rushbrooke, Suffolk, was an English Royalist soldier and politician who was a Member of Parliament between 1604 and 1640.

[1] From 1591 to 1592 he served as a volunteer in the French Wars of Religion, and fought in Henry IV's unsuccessful Siege of Rouen.

[3] In 1604 Jermyn was elected as a Member of Parliament for Andover on the interest of Henry Wriothesley, 3rd Earl of Southampton, with whom he had served in Ireland.

[2] By 1624, Jermyn had become a vocal critic of Spanish policy and on 1 March he argued in the Commons that relations with Spain should be immediately severed.

[1] In 1626 he was on a parliamentary committee which considered Dudley Digges' proposal for a private enterprise war with Spain.

[1] In the 1628 parliament he voted consistently for the king's proposals and his attempts to raise additional taxes.

In the second session, at the grand committee on the customs administration on 23 February 1629, Jermyn sought to discriminate between the misdeeds of officials and the king's commands.

[3] In 1641, he sold his position at court for £2,000 and left the Commons with the intent of retiring, only to be resummoned to parliament in August and November 1642 on suspicion of sending the king money to raise arms.

[2] In the ensuing Civil War he fought as a Royalist, becoming disabled through injury in 1644 and dying in the following year aged 72.