The Ecology Flag was a cultural symbol used in the 1970s by American environmentalists.
Ron Cobb created an ecology symbol which he published on November 7, 1969, in the Los Angeles Free Press and then placed it in the public domain. The symbol was formed by taking the letters "e" and "o", taken from the words "environment" and "organism", and putting them in superposition, thereby forming a shape reminiscent of the Greek letter Θ (Theta). Look magazine incorporated the symbol into an image of a flag in their April 21, 1970 issue. The flag was patterned after the flag of the United States, and had thirteen stripes alternating green and white. Its canton was green with the ecology symbol where the stars would be in the United States flag.