Modular luggage with multiple level modular design and linkable cases

Described herein is a modular luggage system (the "MLS") that includes a modular case system that includes a plurality of interchangeable modular cases having a plurality of interchangeable compartments; a modular transport system that includes a plurality of interchangeable modular transport devices; a first chassis that includes a first chassis inner surface configured to releasably and interchangeably retain an interchangeable modular case selected from the modular case system; and a first chassis frame having attachment regions configured to releasably and interchangeably couple with an interchangeable modular transport device selected from the modular transport system. Also described are a coupling device for a MILS with multiple chassis, and corresponding methods for assembling the above MILS. A kit of parts for assembling the MLS is also described.