Augusta is a city in St. Charles County, Missouri, United States. The population was 270 at the 2020 census, up from 253 at the 2010 census. The city has wineries, antique shops, restaurants, B&B's, a wood shop, a glass studio, massage therapy, a historic museum, and The Augusta Brewery.

St. Charles County is in the central eastern part of the U.S. state of Missouri. As of the 2020 census, the population was 405,262, making it Missouri's third-most populous county. Its county seat is St. Charles. The county was organized October 1, 1812, and named for Saint Charles Borromeo, an Italian cardinal.