Cottleville is a city in St. Charles County, Missouri, United States. The population was 3,075 at the 2010 census.
A post office called Cottleville has been in operation since 1843. The town site was laid out in 1839. It was named by Captain Lorenzo Cottle, an early settler and a veteran of the Black Hawk War and Seminole Wars.
Cottleville is home to Francis Howell Central High School, Louis C. Saeger Middle School and Warren Elementary School. St. Joseph Catholic School is also located in Cottleville, providing classes for grades K-8; St. Joseph Catholic Church is the largest church by number of parishioners in the Roman Catholic Archdiocese of St. Louis.