4585 Ainonai, provisional designation 1990 KQ, is a carbonaceous asteroid from the outer region of the asteroid belt, about 15 kilometers in diameter. It was discovered on 16 May 1990, by Japanese amateur astronomers Kin Endate and Kazuro Watanabe at the Kitami Observatory in eastern Hokkaidō, Japan. The minor planet is named after Ainonai, a small Japanese town located near Kitami in eastern Hokkaidō. The minor planets 3785 Kitami and 3720 Hokkaido are named after these two places. Naming citation was published on 21 November 1991 (M.P.C. 19338).