31641 Cevasco, provisional designation 1999 GW34, is a stony asteroid from the inner regions of the asteroid belt, approximately 3.3 kilometers in diameter. It was discovered on 6 April 1999, by the Lincoln Near-Earth Asteroid Research project (LINEAR) at the U.S. Magdalena Ridge Observatory in Socorro, New Mexico. The S-type asteroid orbits the Sun at a distance of 2.1–2.8 AU once every 3 years and 10 months (1,390 days). Its orbit shows an eccentricity of 0.13 and an inclination of only 1 degree from the plane of the ecliptic.