31824 Elatus (/ˈɛlətəs/; provisional designation 1999 UG5) is a very red centaur from the outer Solar System, approximately 48 kilometers (30 miles) in diameter.

It was discovered on 29 October 1999, by astronomers of the Catalina Sky Survey at Mount Lemmon Observatory in Arizona, United States.

Lightcurve analysis gave a longer-than-average rotation period of 26.5 and 26.82 hours with a concurring brightness variation of 0.10 magnitude (U=2/2).

[8][9] According to observations by ESA's Herschel Space Observatory with its PACS instrument and the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer Elatus measures 49.8 and 57.000 kilometers in diameter and its surface has an albedo of 0.049 and 0.050, respectively.

[6][7] The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous minor planets of 0.057 and derives a diameter of 45.87 kilometers based on an absolute magnitude of 10.42.