Pennsylvanian Period, the geologic period that began about 310,000,000 years ago and lasted 30,000,000 years. It is named for the coal deposits of Pennsylvania, which were formed during the period. Much of the coal of Europe and Asia was formed at the same time. In the United States, major coal deposits of Pennsylvanian age are in the Appalachian region and in a central region extending from Michigan, Illinois, and Iowa to western Kentucky and central Texas.

The Pennsylvanian Period together with the earlier Mississippian Period is commonly referred to as the Carboniferous Period by geologists outside of North America.