Gene Elden Likens is an American limnologist and ecologist. He co-founded the Hubbard Brook Ecosystem Study at the Hubbard Brook Experimental Forest in 1963, and founded the Cary Institute of Ecosystem Studies in Millbrook, New York in 1983.

Limnology is the study of inland aquatic ecosystems. The study of limnology includes aspects of the biological, chemical, physical, and geological characteristics of fresh and saline, natural and man-made bodies of water. This includes the study of lakes, reservoirs, ponds, rivers, springs, streams, wetlands, and groundwater. Water systems are often categorized as either running (lotic) or standing (lentic).