The bear character known for “Only you can prevent forest fires” is Smokey Bear.
Smokey Bear is the U.S. Forest Service mascot created to promote the prevention of human-caused wildfires. The campaign began during World War II, when the Forest Service needed a national symbol after Disney’s Bambi was available only temporarily for fire-prevention publicity. Smokey’s first official campaign appeared in 1944.
The familiar slogan was introduced in 1947 as “Remember... Only YOU Can Prevent Forest Fires.” The wording was officially changed in 2001 to “Only You Can Prevent Wildfires,” because dangerous fires also occur in grasslands and other wild areas, not only forests. The older wording remains the phrase most people associate with the character.
Smokey Bear is often mistakenly called “Smokey the Bear,” partly because a 1950s song added the word “the” for rhythm. His official name has always been Smokey Bear. He was also based loosely on a real rescued American black bear cub found after a 1950 wildfire in New Mexico, though the advertising character and the living mascot were distinct.