Find out about the list of all Ohio state counties in alphabetical order including their county seats, size, numbers. The U.S state of Ohio has 88 counties, here's the full list in alphabetical order: A Adams County (OH) Allen County (OH) Ashland County (OH) Ashtabula County (OH) Athens County (OH) Auglaize County (OH) B Belmont County (OH) Brown County (OH) Butler County (OH) C Carroll County (OH) Champaign County (OH) Clark County (OH) Clermont County (OH) Clinton County (OH) Columbiana County (OH) Coshocton County (OH) Crawford County (OH) Cuyahoga County (OH) D Darke County (OH) Defiance County (OH) Delaware County (OH) E Erie County (OH) F Fairfield County (OH) Fayette County (OH) Franklin County (OH) Fulton County (OH) G Gallia County (OH) Geauga County (OH) Greene County (OH) Guernsey County (OH) H Hamilton County (OH) Hancock County (OH) Hardin County (OH) Harrison County (OH) Henry County (OH) Highland County (OH) Hocking County (OH) Holmes County (OH) Huron County (OH) J ...