Swamp Thing is a 1991 role-playing supplement for DC Heroes published by Mayfair Games.
Swamp Thing is a supplement in which the history of the Swamp Thing is explored, and contains a solitaire adventure.
Shannon Appelcline noted that although Mayfair was closing down their other role-playing lines by 1993, "It looked like DC Heroes might continue, as it was reaching a new creative high in its final years. Swamp Thing (1991), Magic (1992) and Who's Who in the DC Universe 2 (1992) all covered new ground for the game by detailing people and places that were then gelling into DC's new Vertigo universe (1993)."
Gene Alloway reviewed Swamp Thing Sourcebook in White Wolf #32 (July/Aug., 1992), rating it a 3 out of 5 and stated that "I do recommend this as an important work for any individual or group using the Swamp Thing character, or even interested in doing so. They will learn a lot, and have fun as well."