Wentzville is a suburb of St. Louis that is located in western St. Charles County, Missouri, United States. As of the 2010 census, the city had a total population of 29,070. Population estimates in 2019 have placed the city's population at 41,784, making it the 16th largest city in Missouri. Wentzville was the fastest growing city in Missouri between 2000 and 2010 by percentage increased, and population estimates since 2010 indicate that Wentzville is on track to continue as the state's fastest growing city for a second consecutive decade. As the site of the Rotary Park, Wentzville is host to the St. Charles County Fair and the St. Louis Renaissance Festival.
Wentzville was laid out in 1855.