The Fort Simpson Formation is a stratigraphical unit of Devonian age in the Western Canadian Sedimentary Basin.

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Fort Simpson Formation
Stratigraphic range: Late Devonian PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Underlies	Jean Marie Member of the Redknife Formation
Overlies	Muskwa Member of the Horn River Formation
Thickness	up to 1,000 metres (3,280 ft)[1]
Lithology
Primary	Shale
Location
Coordinates	61°07′30″N 120°22′30″W
Region	Alberta  British Columbia  Northwest Territories
Country	Canada
Type section
Named for	Fort Simpson, Northwest Territories
Named by	A.E. Cameron, 1918

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It takes the name from the settlement of Fort Simpson, and was first described in well Briggs Turkey Lake No. 1 (located south-east of Fort Simpson) by A.E. Cameron in 1918.^[2]

The Fort Simpson Formation is composed of grey shale and mudstone.^[1] The shale can be calcareous, silty or sandy.

The Fort Simpson Formation reaches a thickness of over 1,000 metres (3,280 ft) in the sub-surface of the Mackenzie River plain.^[1] It extends from northern Alberta to south-western northwest Territories and in north-eastern British Columbia (north of Peace River Arch).

The Fort Simpson Formation is overlain by the Jean Marie Member of the Redknife Formation in its eastern reaches, and progressively by the Kakisa Formation, Trout River Formation or Tetcho Formation towards the west. It is conformably underlain by the Muskwa Member of the Horn River Formation.^[1]

It is replaced by the Besa River Formation in the Liard River area. It is equivalent to the Imperial Formation to the north, the Tathlina Formation, Twin Falls Formation and Hay River Formation to the east, and the Woodbend Group in Alberta.