It was determined by McDonald's Board of Directors that Steve Easterbrook violated company policy by engaging in the consensual relationship, the company said in a press release. McDonald's did not detail the employee's position in its statement.

Easterbrook apologized for the relationship in a message to staff.

"As for my departure, I engaged in a recent consensual relationship with an employee, which violated McDonald’s policy. This was a mistake," Easterbrook said in an email sent to McDonald's employees and obtained by NBC News. "Given the values of the Company, I agree with the Board that it is time for me to move on. Beyond this, I hope you can respect my desire to maintain my privacy."

Easterbrook has been replaced with Chris Kempczinski, who served as president of McDonald's USA, to lead the company. Kempczinski was has also been elected to the McDonald's Board of Directors.

Kempczinski said in the release that he was thrilled to take over the reins of the multinational corporation.

"We have a responsibility not only to serve great food, but to make it responsibly and to enrich the communities in which we operate," he said. "I am energized by this challenge and look forward to guiding McDonald's continued success."

Enrique Hernandez Jr., chairman of the board, said that Kempczinski was the best person to continue McDonald's performance and lead the corporation forward.

"In particular, Chris was instrumental in the development of the Company's strategic plan, which has enabled global growth and leadership, and has overseen the most comprehensive transformation of the U.S. business in McDonald's history," the chairman said.

Easterbrook said in his email he has full confidence in Kempczinski as he takes over the fast-food giant.

"Please join me in congratulating Chris on his promotion." he wrote. "I know you will support him as you have supported me – he’s lucky to have a team of your calibre."