Great Coasters International, Inc. is a Sunbury, Pennsylvania-based roller coaster manufacturer which has created several award-winning rides since its formation in 1994. Starting in 2006 with Thunderbird at PowerPark in Finland, the company expanded beyond the United States and began building coasters in Europe and Asia. Günter Engelhardt GmbH handles the company's marketing rights in Europe. In addition to building new roller coasters, GCI also refurbishes and re-tracks existing roller coasters, regardless of manufacturer.

Sunbury is a city and the county seat of Northumberland County in Pennsylvania, United States. Located in the Susquehanna Valley, Sunbury is positioned on the east bank of the Susquehanna River.