Last week, Chevrolet said it will also be the automotive partner of Liverpool, a UK rival of Manchester United.
The deals were seen as helping Chevrolet's image globally, especially in Asian markets where the UK's Premier soccer league is popular. Manchester United is the world's most popular soccer team with 659 million fans.
Chevrolet's global rivals, Hyundai and Kia, are both committed to soccer advertising, with long-standing agreements to sponsor the FIFA World Cup and the UEFA European Championship.
Under Ewanick's tenure as global marketing boss, GM scaled back on sports sponsorship in the United States while expanding partnerships in soccer. He pulled GM out of advertising during next year's Super Bowl, the most-watched U.S. sporting event.
GM declined to comment on the reasons for Ewanick's departure other than to say he "failed to meet the expectations the company has of an employee."
Reuters contributed to this report.