Christopher S. Bond, who was Missouri’s youngest governor and the state’s first Republican governor since 1945 when he was elected in 1972, and who went on to serve four terms in the U.S. Senate, died on Tuesday in St. Louis. He was 86.

His death was announced by Gov. Mike Kehoe, a fellow Republican. The announcement did not say where in St. Louis he died.

Mr. Bond, known as Kit, was 31 in 1970 when he was elected state auditor, defeating a 17-year incumbent. He served from 1971 to 1973, when he became governor, having been elected in November 1972 at age 33. He was the first Republican to hold that position since Forrest C. Donnell left office in 1945.

Mr. Bond was defeated for re-election, but he staged a comeback in 1980 by ousting Joseph P. Teasdale, the Democrat who had replaced him. He succeeded Thomas F. Eagleton, a Democrat, in the Senate in 1987 after Mr. Eagleton retired.

His election to a fourth term in 2004 was the seventh time that Mr. Bond won statewide office — more than any other candidate in Missouri’s history.

In 2009, he announced that he would not seek a fifth term in 2010.