Attorney Louis Arthur Johnson (January 10, 1891 - April 24, 1966) was a politician, U.S. cabinet officer, and co-founder of a major law firm. He was born in Roanoke, Virginia, although he spent most of his life in Clarksburg. He was the boxing and wrestling champion at the University of Virginia, where he received his law degree in 1912. Following overseas service in World War I, Johnson helped to found the American Legion and eventually became its national commander.

Johnson was admitted to the bar in Clarksburg in 1913. Later that year, he and John Rixey joined Clarksburg lawyer Phillip Steptoe to establish the law firm of Steptoe, Rixey and Johnson. With the departure of John Rixey in 1914 the firm became Steptoe and Johnson, which remains prominent in the practice of law in West Virginia and the surrounding region.

The American Legion was a potent political force in the years after World War I. Johnson’s election as American Legion national commander in 1932 brought him into a working relationship with the newly elected Roosevelt Administration. President Franklin Roosevelt was the keynote speaker at a Legion conference during Johnson’s term, and in 1936 Johnson involved himself in Roosevelt’s reelection campaign. From 1937 to 1940 Johnson served as assistant secretary of war, advocating for the rearmament of the United States in preparation for World War II. He afterwards resumed the practice of law at Steptoe and Johnson in Clarksburg, although serving briefly in 1942 as Roosevelt’s representative in India.

In the election of 1948, Johnson chaired President Harry Truman's finance committee, which helped engineer Truman's surprise upset victory over Republican Thomas E. Dewey. On March 28, 1949, Johnson was appointed U.S. secretary of defense to succeed the ailing James V. Forrestal. He feuded with other cabinet members and infuriated Truman by openly trying to undermine Secretary of State Dean Acheson, leading Truman to dismiss Johnson in September 1950. Johnson spent most of his remaining years in Washington, where he died.

The Veterans Administration medical center in Clarksburg is named for Louis A. Johnson.