... We present the results of spectrophotometry and BVR CCD photometry, as well as integrated H I radio measurements of a new blue compact galaxy (BCG) HS 0822+3542 with extremely low oxygen abundance: 12 + log(O/H) = 7.35, or 1/36 of solar value. ... This suggests that HS 0822+3542 is one of the nearest and dimmest galaxies experiencing a recently-started first star formation (SF) episode. ... Observations and data reduction . ... Observations . ... H I and dynamical mass . A candidate young galaxy? ...