Ecopath with Ecosim (EwE) is a free and open source ecosystem modelling software suite, initially started at NOAA by Jeffrey Polovina, but has since primarily been developed at the formerly UBC Fisheries Centre of the University of British Columbia.

The NOAA citation states that Ecopath "revolutionized scientists' ability worldwide to understand complex marine ecosystems".

[1] Behind this lie more than three decades of development work in association with a thriving network of fisheries scientists such as Villy Christensen, Carl Walters and Daniel Pauly, and software engineers around the world.

EwE exclusively relies on user involvement for continued software development and releases of new versions.

The computational core of Ecopath with Ecosim can be executed on other operating systems such as Unix or Linux using the Mono common language runtime.