The appellant – identified by the initial "W" -- is a male-to-female transsexual who was refused the right to marry because she did not quality as a "woman" under Hong Kong law.
The Court of Final Appeal ruled the restriction was unconstitutional, but noted the decision did not address the question of same-sex marriage.
The woman, whose sex-change operation was subsidized by the government, had lost her appeal twice before in lower courts.
In a statement issued through her attorney, W said the decision "rights that wrong," the South China Press reported.
"I may have born a man but after transgender surgery at a government hospital more than five years ago, I've lived my life as a woman and been treated as a woman in all respects except as regards my right to marry," she said in the statement.
The court decision won't be effective for 12 months to give Hong Kong lawmakers a chance to address the portion of the law deemed unconstitutional, CNN said.
The majority said the idea a "woman" is a biological standard determined at birth "is particularly hard to justify in the light of significant medical advances in the treatment of transsexualism and important changes in the understanding of and social attitudes towards transsexual persons which have occurred over the last 40-odd years."