NTN Corporation (NTN株式会社 NTN Kabushiki-gaisha) (a.k.a. Niwa, Tomoe, Nishizono) is one of the most prominent manufacturers of bearings in Japan, second domestically only to NSK Limited. The company is one of the largest exporters worldwide of friction-reducing products such as constant-velocity joints. It is listed on the Tokyo Stock Exchange and is a component of the Nikkei 225 stock index.