James Gustave (Gus) Speth (born on March 4, 1942) is an American environmental lawyer and advocate who co-founded the Natural Resources Defense Council.

He served from 1977 to 1981 as a member and then for two years as chairman of the Council on Environmental Quality in the Executive Office of the President.

As chair, he was a principal adviser on matters affecting the environment and had overall responsibility for developing and coordinating the President's environmental program.

[2] In 1982, he founded the World Resources Institute,[3] a Washington, D.C.–based environmental think tank, and served as its president until January 1993.

He was a senior adviser to President-elect Bill Clinton's transition team, heading the group that examined the U.S.'s role in natural resources, energy and the environment.