Sir Thomas Barrington, 2nd Baronet, 1585 to 18 September 1644, was an English politician and Puritan activist who sat in the House of Commons at various times between 1621 and 1644.

In the early stages of the First English Civil War, he helped establish the Eastern Association, one of the most effective elements of the Parliamentarian army.

[5] All three of his brothers-in-law were MPs, as were his father and brother Thomas, making the Barrington family part of a network of Puritan activists.

Barrington has been identified as part of the so-called "Middle Group" within Parliament, led by Pym until his death in December 1643, then by Oliver St John.

Unlike the "War" or "Peace" factions, these MPs did not vote consistently, but they were prominent in persuading Parliament to approve the Solemn League and Covenant, an alliance with the Scots Covenanters.