Blacktail Deer Falls is a 20-foot waterfall on Blacktail Deer Creek in Park County, Wyoming, in the Middle Rockies region. It lies about 34 miles northeast of West Yellowstone and roughly 115.1 miles southwest of Billings as the crow flies.
At 20 feet it is on the modest side for Wyoming, where the typical waterfall with a recorded height stands around 60 feet; it ranks 182nd of 230. By form it is a cascade, descending over a series of rock steps rather than in a single drop.
The Middle Rockies are high, glaciated mountain ranges with alpine peaks, subalpine fir and spruce forest, lodgepole pine and grassy intermontane valleys. Snowmelt streams cascade down glacial valleys and canyon walls.
Park County holds 114 recorded waterfalls, and several are close by. Knowles Falls, a 15-foot cascade waterfall, is about 1.8 miles away across the state line in Montana. Wraith Falls, a 100-foot slide waterfall, is about 3.9 miles away. Undine Falls, a 60-foot tiered waterfall, is about 4 miles away.
Blacktail Deer Falls is located at 44.9869° N, 110.5834° W. The listing is based on the World Waterfall Database, one of the sources compiled by the U.S. Geological Survey in its inventory of waterfalls and rapids of the conterminous United States. The creek name is confirmed against the federal Geographic Names Information System. The position was verified on aerial imagery. Details on trails, parking and access have not been documented for this waterfall yet.