Marinus Willett (July 31, 1740 – August 22, 1830) was an American soldier and political leader from New York City. Marinus was born in Jamaica, New York on Long Island, the great-grandson of Thomas Willett who had immigrated to New York and also served as Mayor of the city.

Marinus Willett fought with the militia during the French and Indian War. He was a lieutenant in General James Abercrombie's expedition to Fort Ticonderoga in 1758. A leader of the Sons of Liberty in New York city, he became Captain in General Richard Montgomery's force, then as Lieutenant Colonel of the 3rd New York Regiment. When the Revolutionary War started, he entered the Continental Army, and Captain Willet accompanied Richard Montgomery in the attempt to capture Canada. He was a member of General Washington's army in New Jersey (1778) and General John Sullivan's in (1779). Elected to the State Assembly for the terms 1780-1784, and as sheriff of New York for 1784-1792. He was appointed as brigadier-general, but declined. He then became Mayor of New York for the period 1807-1808 after De Witt Clinton was removed from office. Willett later became Lieutenant-governor.