Melker Ellborg says "it feels amazing to have signed" for Sunderland for £3m on a deal until summer 2030.
The 22-year-old goalkeeper joins from Malmo and has Champions League and Europa League experience with the 24-time Swedish champions.
"The past few days have been enjoyable," Ellborg said. "From learning about the interest, getting to know the club and the people, and finalising the move.
"The club has had an excellent season so far, and I'm incredibly happy to be part of this journey.
"I'm aware of Sunderland's history, and it means a lot to be part of something with such a rich tradition. I'm really looking forward to meeting everyone at the Stadium of Light on Monday and hopefully playing in front of the fans soon."
Ellborg is not eligible to face Burnley on Monday.
