Richard Michael "Mike" DeWine (born January 5, 1947) is an American politician from Ohio. He currently represents Ohio in the U.S. Senate.

Born in Springfield, Ohio, DeWine earned a bachelor's degree from Miami University in Ohio in 1969 and a Juris Doctor degree from Ohio Northern University. He was a lawyer before entering politics, serving a term in the Ohio State Senate before being elected to the U.S. House of Representatives as a Republican in 1982. He was re-elected three times, serving for a total of eight years.

In 1990 he left the House and was elected Lieutenant Governor of Ohio, and served in that position from 1991 to 1995. After a failed bid to unseat Senator John Glenn in 1992, he was later elected to the U.S. Senate in the election of 1994, defeating prominent attorney Joel Hyatt (the son-in-law of the then-incumbent U.S. Sen. Howard Metzenbaum), and was reelected in 2000, defeating former U.S. Rep. Frank Cremeans in the primary and Ted Celeste (brother of former Ohio Gov. Richard F. Celeste) in the general election.

Hamilton County, Ohio, Commissioner R. Patrick DeWine is DeWine's son. Ohio state Rep. Kevin DeWine (R-Fairborn) is DeWine's second cousin.

In 2004 controversy arose when DeWine fired Jessica Cutler, a female entry-level staff assistant who published a blog detailing numerous sexual exploits. According to the Washingtonienne blog, the staff assistant was supplementing her income by accepting monetary gifts from several older men with whom she was engaged in sexual relationships. The blog, which identified the men only by their initials, stated that one of those men was a chief of staff appointed directly by President George W. Bush.

On May 23, 2005, DeWine was one of 14 senators (see Gang of 14) to forge a compromise on the Democrats' use of the judicial filibuster, thus blocking the Republican leadership's attempt to implement the so-called "nuclear option." Under the agreement, the Democrats would retain the power to filibuster a Bush judicial nominee only in "extraordinary circumstances", and the three of Bush's appellate court nominees (Janice Rogers Brown, Priscilla Owen and William Pryor) would receive a vote by the full Senate.

Some members of the right have expressed the intent to seek revenge against DeWine for his involvement with the filibuster compromise by interfering with the plans of his son Pat to run for a seat in the U.S. House of Representatives. Other speculation centered on DeWine's 2006 primary and the possibility of former U.S. Rep. John Kasich's running against him. On October 4, 2005, Democrat Paul Hackett announced he would challenge DeWine for the seat in the general election