United exercised their option to extend Parris' contract for an additional 12 months earlier this summer in order to avoid her departing on a free transfer.
The 30-year-old joined United in August 2022 from fellow WSL side Arsenal and went on to score 25 goals across 57 appearances for the club.
Brighton head coach Dario Vidosic said: "We're delighted to bring a player of Nikita's ability and experience to the club. It signals our ambition.
"Nikita's record as a goalscorer speaks for itself and she will help us a lot in that regard.
Trending"She is vastly experienced and will be an excellent role model, particularly for our young players.
"She is looking forward to getting stuck into a new challenge and we can't wait to start working with her ahead of our first WSL game next Saturday against Everton."
More to follow...
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