Sir Thomas Monson, 1st Baronet (1565 – 29 May 1641) was an English politician and supporter of King James I.
Sir Thomas was the son of Sir John Monson of South Carlton, Lincolnshire, a past High Sheriff of Lincolnshire. Sir Thomas's younger brother was Admiral Sir William Monson. Thomas was educated at Magdalen College, Oxford, matriculating at the age of fifteen in December 1579, and at Gray's Inn, where he was admitted a student in 1583.
Sir Thomas was appointed a Justice of the Peace in 1592 and High Sheriff of Lincolnshire for 1597 and probably knighted the same year. He then served as a Member of Parliament for Lincolnshire (1597–1598), Castle Rising (1604–1611), and finally Cricklade in 1614.
Under James I Monson thrived. He was made Keeper of the Armoury at Greenwich, Master of the Armoury at the Tower of London and Master Falconer to the King. He was created a hereditary baronet in 1611, one of the first in the Baronetage of England. But in 1615 his position of trust at the Tower of London brought about a situation which led to his arrest as one of the participators in the 1613 murder of Sir Thomas Overbury. He was eventually released however, after a year in the Tower, his reputation and finances ruined.