Marjorie Harris Carr (March 26, 1915 – October 10, 1997) was an American scientist and environmental activist, well known for her conservation work in Florida. She was born in Boston and grew up in southwest Florida, where her parents taught her about native flora and fauna. After earning a Master of Science degree from the University of Florida in 1942, she went on to establish and lead several conservation efforts in the state, including co-founding the Alachua Audubon Society in 1960 and co-founding Florida Defenders of the Environment in 1969. Her work with Florida Defenders of the Environment — which continued until her death in 1997 — to preserve the Ocklawaha River Valley helped halt construction of the Cross Florida Barge Canal, which is now a public conservation and recreation are