Orogeny is the primary mechanism by which mountains are formed on continents. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. This leads to both structural deformation and compositional differentiation of the Earth's lithosphere (crust and uppermost mantle). An orogenic belt or orogen develops as the compressed plate crumples and is uplifted to form one or more mountain ranges; this involves a series of geological processes collectively called orogenesis. A synorogenic process or event is one that occurs during an orogeny.
The word "orogeny" (//) comes from Ancient Greek (ὄρος, óros, lit. ''mountain'' + γένεσις, génesis, lit. ''creation, origin''). Although it was used before him, the term was employed by the American geologist G. K. Gilbert in 1890 to describe the process of mountain-building as distinguished from epeirogeny.