Alexander Porter (June 24, 1785 - January 13, 1884) was a United States Senator from Louisiana. Born in County Donegal, Ireland, he immigrated to the United States in 1801 with an uncle, who settled in Nashville, Tennessee. He received a limited schooling, studied law, was admitted to the bar in 1807 and commenced practice in the Attakapas region of the Territory of Orleans. He was a delegate to the convention which framed the first Louisiana Constitution in 1812 and was a member of the lower branch of the Louisiana Legislature from 1816 to 1818.
Porter was a judge of the State supreme court from 1821 to 1833, and was elected as a Whig to the U.S. Senate to fill the vacancy caused by the death of Josiah S. Johnston and served from December 19, 1833, until January 5, 1837, when he resigned due to ill health. He continued the practice of law in Attakapas and was a planter. Porter was again elected to the U.S. Senate for the term beginning March 4, 1843, but did not take his seat due to ill health; he died in Attakapas in 1844, and interment was on Oakland plantation in Franklin, Louisiana.