Robert W. "Bob" McLean pledged the sum to the Country Music Hall of Fame and Museum to allow the purchase of the 1928 Gibson L-5 guitar and place it permanently in the museum, Nashville's Tennessean reported Tuesday.
Three months ago, the guitar's anonymous owner removed the guitar used by Carter from the country music museum, where it had been on loan since 1998.
The guitar was put up for auction, but the Hall of Fame did not have the funds to buy the instrument.
McLean said he felt compelled to help after reading about the dilemma.
"I knew then and there that I needed to help in that effort," said McLean, an amateur guitar and banjo player and owner of McLean and Company Investments.
McLean's gift was announced Monday at the Hall of Fame, where John Carter Cash, Carter's grandson and son of Johnny Cash and June Carter, and other celebrities, including country singers Vince Gill and Marty Stuart, were on hand.