Henry De Lamar Clayton, Jr. (February 10, 1857 – December 21, 1929) was an American politician and judge from Alabama.
Henry De Lamar Clayton was born near Clayton, Alabama, in Barbour County on February 10, 1857. He attended the common schools and graduated from the literary department of the University of Alabama at Tuscaloosa in 1877 and from its law department in 1878. He was admitted to the bar in the latter year and commenced practice in the town of Clayton. In 1880, he moved to Eufaula, Alabama, and continued the practice of law.
Clayton served as member of the Alabama House of Representatives in 1890 and 1891 and served as United States Attorney for the Middle District of Alabama from 1893 to 1896. He was permanent chairman of the Democratic National Convention in 1908. He was elected as a Democrat to the Fifty-fifth and to the eight succeeding Congresses serving from March 4, 1897 until May 25, 1914. He was chairman of the Committee on the Judiciary (Sixty-second and Sixty-third Congresses) and sponsor of the Clayton Antitrust Act of 1914. He was one of the managers appointed by the House of Representatives in 1905 to conduct the impeachment proceedings against Charles Swayne, judge of the United States District Court for the Northern District of Florida, and in 1912 against Robert W. Archbald, judge of the United States Commerce Court.
Clayton served as a delegate from his home state to the 1912 Democratic National Convention. He then went on to serve in a variety of positions for the Federal Court System and in 1913, was appointed to the U.S. Senate to fill the vacancy caused by the death of Joseph F. Johnston, but his appointment was challenged and withdrawn. On May 2, 1914, Clayton was nominated by President Woodrow Wilson to a joint seat on the United States District Court for the Middle District and Northern District of Alabama, both vacated by Thomas Goode Jones. Clayton was confirmed by the United States Senate on May 2, 1914, and received commission the same day. He then moved to Montgomery to accept this commission, serving as a federal judge until his death.
He died in Montgomery and is buried in Eufaula, Alabama.
His brother, Bertram Tracy Clayton, was also a member of the House of Representatives. Their father, Henry De Lamar Clayton, was a prominent judge and major general in the Confederate army during the American Civil War.
His Clayton, Alabama home, the Henry D. Clayton House, was declared a National Historic Landmark in 1976.