Kirby Corporation is the premier inland tank barge operator in the United States, transporting bulk liquid products throughout the Mississippi River System and the Gulf Intracoastal Waterway. Kirby's service includes the transporting of petrochemicals, pressurized products, black oil products, refined petroleum products and agricultural chemical products by inland tank barge. Kirby also owns and operates four ocean-going barge and tug units transporting dry-bulk commodities in United States coastwise trade.

Through the Kirby Engine Systems segment, Kirby overhauls and services medium-speed and high-speed diesel engines and reduction gears, and sells diesel engine parts through its subsidiary Kirby Engine Systems. Kirby Engine Systems provides these services to distinct segments of the market through its three subsidiaries, Marine Systems, Inc., Engine Systems, Inc. and Rail Systems, Inc. The diesel engines are used in marine, power generation and railroad applications.