Robert Alphonso Taft (September 8, 1889 - July 31, 1953), of the Taft family political dynasty of Ohio, was a United States Senator and Presidential candidate in the United States Republican Party.

Robert Taft was the son of President William Howard Taft. He was educated at Yale University, got his law degree from Harvard University in 1913, and practiced law briefly in Cincinnati, Ohio, his family's ancestral city. During World War I he served on the legal staff of the Food and Drug Administration.

He began his elected political career in the Ohio house of representatives, where he first won a seat in 1921, and served as speaker of the house in 1926. In 1931 he moved to the state senate. He was elected to the first of his three terms as U.S. senator in 1938; he was re-elected again in 1944 and 1950.

As a U.S. senator, he was given the nickname "Mr. Republican"; he was the chief ideologue and spokesperson for the old-fashioned paleoconservatism of the Republican Party of that era. An isolationist, he strove to keep the United States neutral during World War II, and opposed conscription until the attack on the United States at Pearl Harbor in 1942. An active opponent of Franklin Roosevelt's "New Deal," he is famous as the co-sponsor of the Taft-Hartley Act.

He sought nomination as the Republican candidate for President in 1940, but lost to Wendell Wilkie; he again sought the nomination in 1948, but deferred to Thomas E. Dewey; and again in 1952, withdrawing when General Dwight D. Eisenhower announced his candidacy.

Taft died in New York City at the age of 53 and is buried at Indian Hill Episcopal Church Cemetery in Cincinnati. Robert Taft was the father of Robert Taft, Jr (1917-1993), a former member of the United States House of Representatives, and grandfather of Bob Taft, the current governor of Ohio.