Bob Knapp, Costa Mesa's recreation manager, resigned Thursday afternoon after a year and a half on the job.
His last day at City Hall is Friday, according to a city news release.
No reason was given for Knapp's departure. He had no comment when reached by phone.
"The city thanks Knapp for his service to the Costa Mesa community and wishes him well in future endeavors," the release says.
He began the job July 2012 at an annual salary of about $105,000.
Knapp previously worked as a small-business owner. He and his wife, Jennifer, ran Rainbow Magnetics for 15 years before selling the business in 2008.
He came to head the city's recreation division without any previous government experience, though city officials cited his familiarity with the community. Knapp was well known as an active youth sports booster.
"He's uniquely qualified, having run a successful business for years, managing many employees and being deeply involved in and knowledgeable about sports and school activities in our community," city CEO Tom Hatch said in a prepared statement after Knapp's hiring. "He'll give us a fresh look at the services we provide and further develop those relationships."