Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
blissful [ˈblɪsful] adj блаже́нный/блаже́н (event) счастли́вый/сча́стлив
in blissful ignorance в счастли́вом неве́дении
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: