The paleontological collections at the Prairie Research Institute (PRI) are an amalgam of several traditionally independent collections spanning the Illinois Natural History Survey, the Illinois State Geological Survey, and the broader University of Illinois research community. These collections cover a broad scope taxonomically, geographically and temporally, including a wide variety of both marine and terrestrial fossils from strata around the world.

Particular strengths of the PRI paleontological collections include fossil plants and insects from the Pennsylvanian (Upper Carboniferous) of Illinois and a large collection of Midwestern Pleistocene mollusks. In addition, the PRI is also home to the historically significant Milton Sanderson collection of Early Miocene amber from the Dominican Republic as well as a rapidly growing collection of fossil insects from across the globe, ranging in age from Carboniferous to Pleistocene.