The Environmental Council of the States (ECOS) is the national non-profit, non-partisan association of state and territorial environmental agency leaders, established in 1993.

ECOS convenes two general membership meetings per year, a spring membership meeting (Mar 4-6, 2012 in Scottsdale, AZ) and an annual membership meeting (Aug 27-29, 2012 in Colorado Springs, CO). In addition, ECOS hosts multiple project-based meetings.

At the annual meeting, ECOS members confer on environmental matters of importance to the states and come to agreement on positions regarding air, water, waste, compliance, cross-media, and planning.