Alpena County is a county in the U.S. state of Michigan. As of the 2020 census, the population was 28,907. The county seat is Alpena. It is considered to be part of Northern Michigan.

Alpena is a city in the U.S. state of Michigan. It is the county seat of Alpena County, and is the only city within the county. The population was 10,197 at the 2020 census, making it the third most populated city in the Northern Michigan region, after Traverse City and Cadillac. The city is surrounded by Alpena Township, but the two are administered autonomously. It is the core city of the Alpena micropolitan statistical area, which encompasses all of Alpena County and had a total population of 28,907 at the 2020 census.