The Pennsylvanian Allegheny Formation is a mapped bedrock unit in western and central Pennsylvania, western Maryland and West Virginia, USA. It is a major coal-bearing unit in the Ridge-and-Valley Appalachians of the eastern United States.

The Pennsylvanian Allegheny Formation includes rocks from the base of the Brooksville Coal to the top of the Upper Freeport Coal, and was defined to include all economically significant coals in the upper Pennsylvanian sequence.The Geology of Pennsylvania, C. H. Shultz, ed., DCNR Special Publication 1, 1999. (Ch. 10) The formation consists of cyclothemic sequences of coal, shale, limestone, sandstone, and clay. It contains six major coal zones, which, in stratigraphic order, are:

• Upper Freeport Coal
• Lower Freeport Coal
• Upper Kittanning Coal
• Middle Kittanning Coal
• Lower Kittanning Coal
• Brooksville Coal

Relative age dating of the Allegheny places it in the middle Pennsylvanian period.

</ref>