The Environmental Control and Life Support System (ECLSS) is distributed throughout the International Space Station (ISS) pressurized modules. Five International Partners (IP) are designing ECLSS hardware: National Aeronautics and Space Agency (NASA), Russian Space Agency (RSA), European Space Agency (ESA), National Space Development Agency of Japan (NASDA), and one International Participant-Italian Space Agency (ASI). Two U. S. Product Group (PG) contractors are designing ECLSS hardware and outfitting modules. Each contractor has subcontractors and vendors designing hardware. These factors contribute to the magnitude of the ECLSS interface integration across ISS.During assembly of ISS, some pressurized modules change on-orbit locations. All of these interfaces are reviewed and defined, if unique, to ensure compatibility. However, this paper will focus on the final configuration of ISS.ISS is composed of various pressurized modules that provide a variety of capabilities. Some modules are laboratories, such as the United States Laboratory (USL), Japanese Experiment Module (JEM), Attached Pressurized Module (APM), and Research Modules. The Nodes provide interconnectivity. The Habitation (HAB) module provides provisions for the crew. The Mini-Pressurized Logistics Module (MPLM) is temporary and provides resupply capability to ISS. Each has specific purposes and contains various ECLSS functions to support them. This paper provides the ECLSS interface definition between these various modules and defines how the interfaces are controlled.Within the pressurized modules, interfaces are defined between hardware and between contractors to ensure compatibility. This paper defines how these interfaces are controlled.After the interfaces are defined and designed, the interfaces are verified. This paper provides general verification methods. In summary, the paper provides insight into future applications.