Marion Speed Boyd (September 12, 1900 – January 9, 1988) was a United States district judge of the United States District Court for the Western District of Tennessee.

Born in Covington, Tennessee, Boyd received a Bachelor of Laws from the University of Tennessee College of Law in 1921 and entered private practice in Memphis, Tennessee. He was a member of the Tennessee House of Representatives from 1925 to 1927, and was then an assistant state attorney general of Shelby County, Tennessee until 1935. He served in the Tennessee Senate in 1935, and was then a Referee in Bankruptcy for the United States District Court for the Western District of Tennessee from 1935 to 1937. He was a Judge of the City Court of Memphis from 1937 to 1938, and state attorney general of Shelby County from 1940 to 1961.^[1]

On September 13, 1940, Boyd was nominated by President Franklin D. Roosevelt to a seat on the United States District Court for the Western District of Tennessee vacated by Judge John Donelson Martin Sr. Boyd was confirmed by the United States Senate on September 18, 1940, and received his commission on September 27, 1940. He served as a member of the Judicial Conference of the United States from 1960 to 1963, and as Chief Judge from 1961 to 1966, assuming senior status on August 1, 1966 and continuing in that capacity until his death on January 9, 1988.^[1]

• List of United States federal judges by longevity of service