Slough Creek is a tributary of the Lamar River, approximately 25 mi (40 km) long, in Montana and Wyoming in the United States.

A myth associated with the name involves a U.S. Army enlisted man who was escorting an exploring party in 1873 and got lost in the valley.

Trumpeter John P. Slough of Company I, Second Cavalry wrote this in his diary:[2] We attempted to follow the Hayden trail to ascertain where he had crossed the Yellowstone River below the lake.

It rises in southern Montana, in the Absaroka-Beartooth Wilderness in the Beartooth Mountains, and flows southwest, into Yellowstone National Park and into Wyoming.

Cutthroat trout in Slough offer good dry fly fishing with heavy hatches of caddis, pale morning duns, and large Green Drakes in July.

Slough Creek is not usually fishable until about the second week of July, because of high water, so check conditions by contacting local fly stores The National Park Service has made frequent changes to the regulations for Slough Creek, and in 2018 has made significant new changes.