The move came after a new law went into effect July 16 allowing people to change their registered sex if they've had a sex-change operation and have been diagnosed by at least two doctors as having gender-identity disorder. Applicants must be aged 20 or older, unmarried with no children and not be able to reproduce.
The Naha Family Court approved an application Wednesday to allow the woman to change her sex in her official family registry from male to female, a court official said on condition of anonymity.
The Asahi Shimbun newspaper quoted the court ruling as saying that the plaintiff "does appear to be suffering from great psychological pain ... and recognizes the necessity of obtaining a stable, female identity."
Kyodo News reported that growing up, the plaintiff had been uncomfortable with her gender and last year underwent a sex-change operation.
Due to privacy concerns, the woman has only been identified as a resident of Japan's southernmost prefecture (state) of Okinawa in her 20s.
Ran Yamamoto, who heads a Tokyo-based support group for transsexuals, described Wednesday's developments as a "big step forward," but said further changes were needed.
"It doesn't mean that this is the end of the battle,'' Yamamoto said, because the stipulations bar many transsexuals from officially changing their registered sex, forcing them to continue enduring discrimination and social stigma.
At least 15 applications had been lodged by transsexuals wanting to change their recorded gender and more are expected following Wednesday's decision, Yamamoto said.
He said there are an estimated 7,000 to 10,000 people in Japan with gender identity disorder -- that they believe they were born the wrong sex.