Alexander O. Anderson (November 10, 1794–May 23, 1869) was an attorney from Tennessee who briefly served as a Democrat in the United States Senate.

The son of longtime U.S. Senator Joseph Anderson, he was born at his father's home, "Soldier's Rest", in Jefferson County, Tennessee. As a youth he graduated from Washington College in Greeneville, Tennessee. He volunteered for service in the War of 1812 and fought under Andrew Jackson in the famous Battle of New Orleans in 1814. Later in that year he was admitted to the bar, and began a practice in Dandridge, Tennessee. Afterwards he moved to Knoxville, and then served as the superintendent of the United States Land Office in Alabama in 1836. He was an agent in the Indian Removal of 1838 from Alabama and Florida.

He was elected to the United States Senate by the Tennessee General Assembly to the vacancy caused by the resignation of Senator Hugh L. White, serving in that body from February 26, 1840 to March 3, 1841, when the term expired. Anderson did not stand for reelection to the seat; it was to remain vacant for a period when a group of Tennessee Democratic legislators called the "Immortal Thirteen" refused to meet and give a qurorum sufficient to allow the election of a successor, apparently preferring no representation to that by a member of the other party (Whigs).

Anderson was a leader of an overland company going to California in 1849. He served in the California State Senate in 1850 and 1851, and then as a judge on the California Supreme Court from 1851 to 1853 before returning to Tennessee. He later practiced law in Washington, DC, appearing before both the United States Court of Claims and the Supreme Court of the United States. During the American Civil War he returned to Alabama, practicing law in Mobile and Camden. Again returning to Tennessee, he died in Knoxville and is buried in the Old Gray Cemetery.