William Brown Maclay (March 20, 1812 - February 19, 1882) was a United States Representative from New York. Born in New York City, he received private instruction and was graduated from the College of the City of New York in 1836. He was associate editor of the New York Quarterly Review in 1836, taught Latin, studied law, was admitted to the bar in 1839 and commenced the practice of his profession in New York City. He was a member of the New York State Assembly from 1840 to 1842 and was elected as a Democrat to the Twenty-eighth, Twenty-ninth, and Thirtieth Congresses, holding office from March 4, 1843 to March 3, 1849. He was an unsuccessful candidate for reelection in 1848 to the Thirty-first Congress, and was elected to the Thirty-fifth and Thirty-sixth Congresses, holding office from March 4, 1857 to March 3, 1861. He was not a candidate for reelection in 1860 to the Thirty-seventh Congress, and in 1882 died in New York City. Interment was in Green-Wood Cemetery, Brooklyn.
| Preceded by Aaron Ward |
Member of the U.S. House of Representatives from New York's 4th congressional district 1843–1849 |
Succeeded by Walter Underhill |
| Preceded by Thomas R. Whitney |
Member of the U.S. House of Representatives from New York's 5th congressional district 1857–1861 |
Succeeded by William Wall |