The St. Louis Limestone is a large geologic formation covering a wide area of the midwest of the United States.

It consists of sedimentary limestone with scattered chert beds, including the heavily chertified Lost River Chert Bed in the Horse Cave Member.

The limestone deposit is Mississippian in age, in the Meramecian series, roughly 330-340 million years old.

Fossils commonly found in the St. Louis include the rugosan corals Lithostrotion and Lithostrotionella and the bryozoan Fenestrellina.

This article about a specific stratigraphic formation in the United States is a stub.