Jadzia, a humanoid host of Dax, a symbiont on Star Trek: Deep Space 9
Jadwiga -- a fictional Nazi death camp in the 1974 TV mini-series "QB-VII" (and same-titled book by author Leon Uris).
Jadwiga, a ghost in Esther Friesner's trilogy, Gnome Man's Land. Mother of Yang, a Mongolian ancestral spirit who in life had been the leader of the fictional Cerise Horde after killing her husband when she refused sexual advances. Apparently can do wonderful things with dog meat.