The Legion Lake Fire was a wildfire that occurred in December 2017 in the Black Hills of South Dakota, United States.

[4] Additionally, low humidity, high winds, and unseasonably warm weather allowed the fire to grow quickly.

[7] Firefighting efforts brought the fire up to 50% containment by December 14, at which point evacuation orders were lifted, but the parks remained closed.

[4][8] Overall, the fire burned 53,875 acres (218.02 km2), making it the third-largest wildfire in both South Dakota[1] and Black Hills history.

[1] In 2018, the park was awarded a $1.8 million grant to aid in recovery efforts, which covered costs related to reseeding and weeding the burn scar.

[12] In August 2018, several people whose land had been burned in the fire filed a lawsuit against Black Hills Power and Hanson Communications, alleging that the installation of the power line had damaged a tree's root system, causing it to fall onto the line and begin the fire.