NGC 4639 is a barred spiral galaxy located in the equatorial constellation of Virgo.

John L. E. Dreyer described it as "pretty bright, small, extended, mottled but not resolved, 12th magnitude star 1 arcmin to southeast".

[10] The morphological classification of this galaxy is SAB(rs)bc,[5] indicating a spiral galaxy with a weak bar (SAB), an incomplete ring around the bar (rs), and moderate to loosely-wound spiral arms (bc).

NGC 4639 has a mildly active galactic nucleus of the Seyfert type 1; one of the weakest known.

The compact central source has been detected by its X-ray emission, and is variable on timescales of months to years.