The 19-year-old joins the club following the conclusion of her contract at Swiss side FC Basel and can play in a variety of attacking positions. Fuso has also previously played for SC Freiburg in the Frauen-Bundesliga.
Fuso has represented the German national team at various age groups and is currently Under-19 captain.
Ivana Fuso said:
“I’m so happy to be here, it’s a dream to sign for a club like Manchester United. Casey is a great coach and I’m looking forward to working with her and the staff, as well as meeting my new team-mates.
“It will be my first time playing in England, the league is very competitive and I know that being a part of this team will help me develop further as a player.