The redshift of the highly variable BL Lac object H 0323+022.

New optical spectra are used to derive the redshift of H0323+022, a bright, highly variable X-ray source whose nature has been subject of controversy. Most of the spectra are dominated by a featureless nonstellar continuum, as found in BL Lac objects. Photometric variations of ⪆2 mag have been seen over a time interval of only 2 days. The nonstellar light is sometimes faint enough to allow the detection of absorption lines at a redshift z = 0.1471±0.0005. These lines are clearly due to stars in the host galaxy, which is easily visible in deep images of the object. The galaxy is probably a relatively normal elliptical with M_V ≈ -21 to -22, except that a noticeable extension is evident in one quadrant. There is now no doubt that H0323+022 is a BL Lac object, rather than a peculiar Galactic star.