Chessie System, Inc. was a holding company that owned the Chesapeake and Ohio Railway (C&O), the Baltimore and Ohio Railroad (B&O), the Western Maryland Railway (WM), and several smaller carriers. It was incorporated in Virginia on February 26, 1973, and acquired the C&O (which controlled the other companies) on June 15. On November 1, 1980, Chessie System merged with Seaboard Coast Line Industries to form CSX Corporation.

Headquartered in Cleveland, Ohio, the Chessie System was the creation of Cyrus S. Eaton and his protégé Hays T. Watkins, Jr., then president and chief executive officer of the C&O. A chief source of revenue for the Chessie System was transportation of coal mined in West Virginia.

The signature symbol of the Chessie System was its "Ches-C", a large emblem incorporating the outline of the C&O's famous "Chessie" the kitten logo. The Ches-C was emblazoned on the front of all Chessie System locomotives, and also served as the "C" in "Chessie System" on the locomotive's flanks, and on other rolling stock. The Chessie System itself did not own any locomotives or other rolling stock; rather, equipment would be placed on the roster of one of the three component railroads. While all three companies shared a common paint scheme of yellow, vermillion, and blue, actual ownership of the equipment was denoted by the reporting marks: C&O, B&O, or WM.