Racer (Kennywood) in the context of "Roller coaster"

A roller coaster is a type of amusement ride employing a form of elevated railroad track that carries passengers on a train through tight turns, steep slopes, and other elements. Roller coasters are usually designed to produce a thrilling experience, though some roller coasters aim to provide a more gentle experience. Trains consist of open cars connected in a single line, and tracks are typically built and designed as a complete circuit in which trains depart from and return to the same loading station. One notable exception is Racer at Kennywood, West Mifflin, PA, which has the train return to the opposite loading track due to its unique Möbius design. The rides are typically found in amusement parks around the world but can also be located in shopping malls and zoos. The Roller Coaster DataBase estimates there are approximately 6,000 extant roller coasters as of October 2025.

The earliest progenitors to the modern roller coasters were the "Russian Mountains", which first appeared in the 17th century. LaMarcus Adna Thompson obtained one of the first known patents for a track-based roller coaster design in 1885, based on the Switchback Railway which opened a year earlier at Coney Island. Today, most roller coasters are built out of steel, which can allow for more intense forces and inversions (where the rider is upside down).