NGC 5173 is a peculiar elliptical galaxy in the northern constellation of Canes Venatici. It was discovered May 12, 1787 by German-British astronomer William Herschel. This galaxy has an apparent visual magnitude of 12.2, and spans an angular size of . It is the second brightest member of a small group of galaxies, with the brightest being NGC 5198; it lies at the eastern edge of its group. NGC 5171 is separated from the nearby Sb galaxy NGC 5169 by just , and they have a velocity difference of .
Originally, this was classified by de Vaucouleurs as an elliptical galaxy, having a morphological classification of E0: which indicates a spherically-symmetric shape. In 1984, neutral hydrogen gas was discovered in NGC 5171, with a mass estimated at being about double that of gas-rich ellipticals.
Observations reported in 1991 showed the presence of a star-forming spiral structure located off-center from the galaxy isophotes. This may be the remnant of an accreted galaxy similar to the Large Magellanic Cloud, with at least 10âÂÂ20% of the original galaxy's mass. The disk has a radial extent of about . Massive clusters have formed in this disk over the last 400 Myr. Observations with the Hubble Space Telescope show filamentary structures at the center of the galaxy.