Lion's Den Gorge Nature Preserve is a 73-acre public park located in Ozaukee County, Wisconsin, running adjacent to Lake Michigan for 0.7 miles near the village of Grafton and city of Port Washington. It was purchased by the county in 2002 from a private property owner and borders a 44-acre United States Fish and Wildlife Service waterfowl production area. The gorge was named after an animal the had escaped from the Milwaukee County zoo and spent several nights in the area.