'Miggy' arrived at St. James' Park for a then-club-record fee in January 2019 and has gone on to make 223 appearances for Newcastle United.
The popular Paraguayan found the net on 30 occasions during his six years on Tyneside and played a significant role as Eddie Howe's side reached the Carabao Cup final and finished fourth in the Premier League during the 2022/23 season.
He subsequently opened the scoring during the first UEFA Champions League game at St. James' Park in more than 20 years in October 2023 as the Magpies thrashed French champions Paris Saint-Germain 4-1.
Newcastle United head coach, Eddie Howe, said: "On behalf of the club, I want to thank Miggy for everything he has given us during our time together.
"He has been the ultimate professional, and he has been a big part of some of our most memorable moments in recent seasons.
"He is a great person and we'll miss him greatly, but this is the right move at the right time for him and his family and we wish them well."