Easterbrook was replaced by Chris Kempczinski, the president of McDonald's USA. Kempczinski was also elected to the board of directors.
"Easterbrook... has separated from the company following the board's determination that he violated company policy and demonstrated poor judgment involving a recent consensual relationship with an employee," the company said in a statement.
There were no additional details of his ouster, and whether he was fired or allowed to resign.
Kempczinski "has the right mix of skills and experience to lead us forward having run our US business, where franchisees are delivering strong financial and operational results, and overseen global strategy, business development and innovation," the company quoted Enrique Hernandez Jr, chairman of McDonald's board of directors, as saying.
In its most recent earnings report, on October 22, McDonald's said profits dipped 1.8 percent in the third quarter from the year-ago period to $1.6 billion. Revenues edged up 1.1 percent to $5.4 billion.
The fast-food giant notched a healthy 5.9 percent increase in global comparable sales, including a solid rise in the United States.
But profits were pressured by increased spending on technology and research and development.
McDonald's has invested heavily in home-delivery and mobile pay initiatives in recent years, and in 2019 has unveiled a number of acquisitions to boost its drive-through operation.
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