Imperial is a census-designated place (CDP) in Jefferson County, Missouri, United States. The population was 4,709 at the 2010 census, up from 4,373 in 2000. It was originally known as West Kimmswick, and is located 22 miles (35 km) south of downtown St. Louis. St. John's Church is a historic parish church located within Imperial.
Imperial is located in northeastern Jefferson County at 38°22′15″N 90°22′24″W. According to the United States Census Bureau, the CDP has a total area of 6.04 square miles (15.65 km2), of which 5.25 square miles (13.61 km2) are land and 0.79 square miles (2.04 km2), or 13.01%, are water.
Imperial is bordered to the north by Arnold, to the south by Barnhart, and to the east by the Mississippi River, which forms the Illinois state line. The CDP surrounds the city of Kimmswick. Interstate 55 runs through Imperial, with access from Exits 185 (Secondary Route M) and 186 (Main Street).