The Dagny Johnson Key Largo Hammock Botanical State Park is a state park in Key Largo, Florida. It is best noted for being an important home for the threatened Key Largo Wood Rat and Key Largo Cotton Mouse, among around 80 other protected species.

The Dagny Johnson Key Largo Hammock Botanical State Park was originally slated to become a condominium project known as Port Bougainville. The project got into financial issues, however, so they decided to sell the land instead. This helped established the state park and preserve the home to numerous species of flora and fauna.

Activities that can be enjoyed at the site include biking, picnicking, hiking, and wildlife viewing. Ranger-guided tours around the site are also available.