The full-back has previously represented San Diego Wave and Atletico Madrid as well as Hammarby and AIK in her homeland.
Lundkvist, 23, has already been capped 17 times by Sweden and started every game at the 2025 UEFA Women's European Championship.
Hanna Lundkvist said: “I am really excited to be here; Manchester United is a club with an amazing history. You can feel how much they have grown in the last few years, competing in one of the strongest leagues in the world and performing in the Champions League.
“Speaking with Marc and the coaches confirmed all of the great things I have heard about the culture of the team here.