Belopolskya (minor planet designation: 1004 Belopolskya), provisional designation 1923 OS, is a dark Cybele asteroid from the outermost region of the asteroid belt, approximately 75 kilometers (47 mi) in diameter. It was named for Russian astrophysicist Aristarkh Belopolsky.

Belopolskya was discovered on 5 September 1923, by Russian astronomer Sergey Belyavsky at Simeiz Observatory on the Crimean peninsula.^[8] Eight nights later, the body was independently discovered by Karl Reinmuth at Heidelberg in Germany.^[2]

It was first identified as A917 TA at Simeiz in 1917. The body's observation arc begins with the above-mentioned Heidelberg-observation following its official discovery.^[8]

Belopolskya orbits the Sun at a distance of 3.1–3.7 AU once every 6 years and 3 months (2,292 days). Its orbit has an eccentricity of 0.09 and an inclination of 3° with respect to the ecliptic.^[1] With these orbital parameters, it belongs to the Cybele asteroids, a dynamical group named after one of the largest asteroids, 65 Cybele.

Belopolskya is classified as a PF-type asteroid in the Tholen taxonomy, a subtype of the dark and reddish P-type asteroids. A few dozens of these bodies are known, most of them are Jupiter trojans or reside in the outermost main-belt.^[9]

This minor planet was named in honor of Aristarkh Belopolsky (1854–1934), astrophysicist at Pulkovo Observatory, the principal astronomical observatory of the Russian Academy of Sciences, which is located south of Saint Petersburg in Russia. Belopolsky is also honored by the lunar crater Belopol'skiy.^[2] Naming citation was first mentioned in The Names of the Minor Planets by Paul Herget in 1955 (H 96).^[2]