William Alexander Duer (September 8, 1780 – May 30, 1858) was an American lawyer, jurist, and educator from New York City who served as the President of Columbia University from 1829 to 1842.

In addition to practicing law, he contributed to a partisan weekly paper called the Corrector, conducted by Peter Irving in support of Aaron Burr.

He next opened an office in Rhinebeck, and in 1814 was elected to the New York State Assembly, where he was appointed chairman of a committee on colleges and academies, and succeeded in passing a bill, which is the original of the existing law on the subject of the common-school income.

He was also chairman of the committee that arranged the constitutionality of the state law vesting the right of navigation in Livingston and Robert Fulton, and throughout his service bore a prominent part in promoting canal legislation.

He was the author of two pamphlets addressed to Cadwallader D. Colden on the "Steamboat Controversy," and the "Life of William Alexander, Earl of Stirling" (New York, 1847).