1633 Chimay, provisional designation 1929 EC, is a Themistian asteroid from the outer region of the asteroid belt, approximately 37 kilometers in diameter. It was discovered on 3 March 1929, by Belgian astronomer Sylvain Arend at the Royal Observatory of Belgium in Uccle. Five nights later, the body was independently discovered by Max Wolf at Heidelberg Observatory in southern Germany.
Chimay is a member of the Themis family, a dynamical family of outer-belt asteroids with nearly coplanar ecliptical orbits. It orbits the Sun at a distance of 2.8–3.6 AU once every 5 years and 9 months (2,085 days). Its orbit has an eccentricity of 0.12 and an inclination of 3° with respect to the ecliptic. Chimay was first identified as A917 BB at Heidelberg in 1917, extending the body's observation arc by 12 years prior to its official discovery observation.
Several rotational light-curve were obtained from photometric observations. They gave a well-defined, concurring rotation period of 6.58–6.63 hours with a brightness variation between 0.31 and 0.58 magnitude (U=3/3-/2).
According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Chimay measures between 36.1 and 37.7 kilometers in diameter, and its surface has a low albedo between 0.079 and 0.089. In accordance with the space-based surveys, the Collaborative Asteroid Lightcurve Link (CALL) derives an albedo of 0.078, and calculates a diameter of 36.1 kilometers. CALL also classifies Chimay as a S-type rather than a carbonaceous C-type asteroid.
The minor planet was named after the Belgian town Chimay, home of the discoverer, who also co-discovered Comet Arend–Roland. Naming citation was published before November 1977 (M.P.C. 3931).