The defending national champion Buckeyes received all 61 first-place votes from the media panel in the rankings released Sunday.
TCU is No. 2, followed by Alabama, Baylor and Michigan State.
The Buckeyes won the first College Football Playoff championship last season and are trying to become the 12th team to win consecutive AP titles since the poll began in 1936.
Preseason rankings date back to 1950. Since then, no team had received more than 97 percent of the first-place votes in a preseason poll.
In 2013, Alabama, which had won two straight championships, received 58 of 60 first-place votes, and defending champion Florida did the same in 2009. Neither finished the season No. 1.
This is the eighth time Ohio State has been named the AP preseason No. 1, but the Buckeyes have not won a national championship in any of the previous seven years it happened. They finished No. 2 in both 1998 and 2006 after being ranked No. 1 at the start of the year.
The rest of this year's preseason top 10 is Auburn, Oregon, USC, Georgia and Florida State.
The Associated Press and ESPN Stats & Information contributed to this report.
Ohio State unanimous No. 1 in AP poll
Heather Dinich reacts to the preseason Associated Press college football poll rankings, which has Ohio State as the No. 1 team.
Buckeyes unburdened by expectations
Despite coming off a national title and starting the season ranked No. 1, Ohio State players say they don't feel the pressure of the outsized expectations placed on them.
Davis: Ohio State the clear national title favorite
College football analyst Butch Davis says Ohio State is the clear favorite to win the national championship.