Suffolk County Legislator Rudy Sunderman will resign from his seat next month to become deputy director of the Suffolk County Fire Academy.
Sunderman is a Republican who represents Shirley.
He said his decision had "nothing to do" with a criminal case against him. Sunderman has pleaded not guilty to felony perjury charges for allegedly lying to the Suffolk County Board of Ethics about working two government jobs.
Sunderman has also served as the Mastic Fire Department chief for 34 years.
The pending charges do not require Sunderman to step down as legislator.
A special election will be held within 90 days of the vacancy for the remainder of his term, which ends in December.