Roush Performance is an American automotive company primarily involved in the engineering, development, and manufacturing of high-performance components for street and competitive racing applications.

In addition to the high performance business, Roush supplies propane conversions kit for the F-150, as well as for school buses.

Perhaps best known of these Roush-modified vehicles is the Ford Mustang, which in 2016 is available in the "RS" (3.7 liter V6, with body kit, stripes, wheels, and interior modifications only), "Stage 1" (standard 5.0 liter V8, with body kit, stripes, wheels, and interior modifications only), "Stage 2" (standard 5.0 liter V8, with body kit, stripes, wheels, suspension, and interior modifications only), and "Stage 3" (body kit, stripes, wheels, suspension, interior, and exhaust modifications, with the addition of an Eaton-supplied 2.3 liter TVS-2300 "roots-style" supercharger).

The addition of the supercharger to the Ford-supplied 5.0 liter engine on the Stage 3 version results in a horsepower output of 670.

Roush has been modifying factory-born Ford Mustangs since 1995 on a limited-run basis, and made several numbered, limited-edition models: All models are serialized with a unique plaque and other documentation (some as "limited edition" vehicles), and are registered with Roush Performance in order to avoid cloning.