The Republican represented the 37th District, which includes several suburbs like Mokena, Orland Park and Joliet.
Ozinga did not give a reason for his resignation, but released a statement, which reads, in part, "As of today, my service in the Illinois House will end. However, I will continue to dedicate my time and efforts to make Illinois a better place. I remain committed to advocating for the people of my district and moving the State of Illinois in the right direction."
A committee is accepting applications to fill the seat until noon on Friday. They will then meet that afternoon to vote on a replacement.
Ozinga will stay on as the chairman for Will County Republicans.