Louis Leon Ludlow (June 24, 1873 – November 28, 1950) was a Democratic Indiana congressman; he proposed a constitutional amendment early in 1938 requiring a national referendum on any U.S. declaration of war except in cases of direct attack.

Congress rejected the Ludlow Amendment only by a narrow margin and after an appeal from President Franklin Delano Roosevelt.

He was married on September 17, 1896, to Katherine Huber of Irvington, Indiana, the society editor on the Sentinel in Washington.

He was buried in Rock Creek Cemetery in Washington, DC and was survived by his wife and four children, Margery, Blanche, Virginia, and Louis.

Ludlow was a Washington correspondent for Indiana and Ohio newspapers (the Indianapolis Star, the Star League of Indiana, the Columbus Dispatch, and the Ohio State Journal) and a member of the Congressional Press Galleries from 1901 to 1929.