The court ruled Friday that the state’s district lines are unconstitutionally gerrymandered to favor Republicans.
Ohio is also being ordered to draw a new map for the 2020 election.
The court also wants to know how state lawmakers determine the new boundaries.
Ohio Attorney General Dave Yost says the state will appeal.
Similarly, a court threw out Michigan’s congressional map last week.
The fate of the maps in Ohio and Michigan likely depends on how the Supreme Court handles gerrymandering cases in two other states: Maryland and North Carolina.