The Onex, Sonex, Waiex and Xenos are a family of lightweight, metal, low-wing, two seat homebuilt aircraft. Kits are produced and marketed by Sonex Aircraft, a small manufacturer based in Oshkosh, Wisconsin. By 2014, 500 customer built aircraft had been completed. The Sonex can also be built from plans.

Sonex Aircraft, LLC is an American kit aircraft manufacturer located in Oshkosh, Wisconsin, producing kits for four all-metal homebuilt monoplanes. The company was founded in 1998 by John Monnett, who has designed the Monnett Sonerai sport aircraft series, Monnett Monerai sailplane, Monnett Moni motorglider, and Monnett Monex racer. Monnett designs are displayed in the Steven F. Udvar-Hazy Center of the National Air and Space Museum near Washington D.C.