331 Etheridgea is a large main belt asteroid. It was discovered by Auguste Charlois on 1 April 1892 in Nice. The meaning of the name is unknown. This asteroid is orbiting the Sun at a distance of with a period of and an eccentricity (ovalness) of 0.10. The orbital plane is tilted at an angle of 6.05ð to the plane of the ecliptic.
Analysis of the asteroid light curve generated from photometric data collected in 2015 provided a rotation period of . This result is completely different from the previous rotation period estimates. It is a low albedo, carbonaceous C-type asteroid and spans a girth of .
It may have been named for the geologist and paleontologist Robert Etheridge (1819âÂÂ1903).