Frank Bartlett Willis (December 28, 1871 – March 30, 1928) was an American politician and lawyer.

After teaching at Ohio Northern for twelve years, Willis was admitted to the bar and began practicing law.

After placing Warren Harding's name in nomination at the 1920 Republican National Convention, Willis was elected to the U.S. Senate in 1920, replacing Harding, who then resigned his Senate seat to take the presidency, allowing Willis to take his seat early.

[1] He died in office that year at Gray Chapel, Ohio Wesleyan University, in Delaware, Ohio, during a Republican Party event for his candidacy organized by the Delaware County Willis-for-President Club.

Willis's official papers were donated to and are open for research at the Ohio History Center.