Doanld Trump is ahead in the Buckeye state.
With 42 per cent of the votes counted, the New York tycoon was leading Ms Clinton 52-44, according to early results broadcast by CNN.
Ohio is one of the ultimate swing states, and it is all but but Mr Trump to win the White House without securing Ohio.
Ohio has 18 electoral votes up for grabs, while 270 are needed for a candidate to win the presidency.
Cleveland was the site of the Republican National Convention in July.
Ohio Republican US senator Rob Portman has won re-election over Democratic ex-governor Ted Strickland.
Nearly 11,000 more voters cast ballots before election day in 2016 compared to 2012, state officials said on Monday night.
Overall close to 1.8 million people voted early in the state.
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