NHK projects that Okinawa Governor Tamaki Denny is certain to win a second term in Sunday's election.
The projections are based on exit polls and information collected before the vote.
The 62-year-old Tamaki ran as an independent and was supported by opposition parties.
His main rival was former Ginowan mayor Sakima Atsushi, who was supported by the ruling coalition.
Tamaki is a former Lower House lawmaker and radio personality.
He was first elected governor in the 2018 election that was held after the death of former governor Onaga Takeshi.
During the campaign, Tamaki reiterated his opposition to the central government's plan to relocate the US Marine Corps Futenma Air Station within the prefecture. He also stressed his achievements during his first term, such as addressing child poverty.