Caleb Brewster (September 12, 1747 – February 13, 1827) was a member of the Culper spy ring during the American Revolutionary War, reporting to General George Washington through Major Benjamin Tallmadge. Brewster not only carried messages to and from the Ring's main spies in Setauket, New York and New York City across Long Island Sound from and to Tallmadge, but made some direct reports to Washington concerning naval activities in the New York City area. Abraham Woodhull and Robert Townsend, alias "Samuel Culper, Sr." and "Samuel Culper, Jr." respectively, were the main agents in the Ring. Tallmadge was referred to by the alias "John Bolton." As a Continental Army officer serving under Tallmadge, Brewster also participated in military actions.
Brewster was born in Setauket, New York, a hamlet now part of the town of Brookhaven. He was the son of Benjamin Brewster, grandson of Daniel Brewster, and great-grandson of the Rev. Nathaniel Brewster (the first minister of the old town church in Setauket).
After the Revolutionary War, Brewster was a blacksmith, an officer in the United States Revenue Cutter Service for 20 years and a farmer.