Concept2 is a manufacturer of rowing equipment based in Vermont, USA. It is best known for its air resistance indoor rowing machines (a.k.a. "ergometers" or "ergs"), which are considered the standard training and testing machines for competition rowers and can be found in most gyms.
Competitive events rowed on a Concept2 rower include: the CRASH-B Sprints (which style themselves the world championship for indoor rowing); the British Indoor Rowing Championships indoor rowing competitions; and the CrossFit Games events (including the CrossFit Open and qualifiers). Concept2 also manufactures oars for sculling and sweep rowing (under the name Dreissigacker) and air resistance Nordic skiing trainers (SkiErgs).