Sulphide Lake is located in North Cascades National Park, in the U. S. state of Washington.

[2] Sulphide Lake lies in a cirque on the southeast slopes of Mount Shuksan.

After Sulphide Creek drains from Sulphide lake, it then plunges at least 2,000 ft (610 m) over a series of cascades called Sulphide Creek Falls, which is one of the tallest waterfalls in the U.S.[3] The lake is in a basin with near vertical walls and the rock is phyllite and greenschist.

Above the lake on the cliffs below Crystal Glacier a 0.3 mile wide band stained red in color (from iron oxide) is exposed that runs for about 2.5 miles.

This band is rich in the iron sulfides pyrite and pyrrhotite.