Alexander Cummings McWhorter Pennington, Sr. (July 2, 1810, Newark, New Jersey – January 25, 1867, New York City) was an American Whig Party / Opposition Party politician who represented New Jersey's 5th congressional district in the United States House of Representatives from 1853 to 1857.

Born in Newark, New Jersey, July 2, 1810, he attended the United States Military Academy, West Point, New York, from 1826 to 1828.

He went on to study law, was admitted to the bar in 1833, and commenced practice in Newark.

He served as chairman of the Committee on Foreign Affairs in the Thirty-fourth Congress.

After leaving the Congress, he moved to New York City, where he died January 25, 1867.