Lee scored six goals in 36 La Liga games for Mallorca last season
The midfielder, 22, who spent two years with the Spanish side, has signed a five-year-deal with the French champions.
Lee is PSG's fourth summer signing after midfielder Manuel Ugarte, central defender Milan Skriniar and striker Marco Asensio.
"It's incredible to be able to join Paris St-Germain," he said.
"It's one of the biggest clubs in the world, with some of the greatest players in the world. I can't wait to start this new adventure."
Lee has been capped 19 times by South Korea and played at the 2022 World Cup.
Former Spain and Barcelona coach Luis Enrique took over as PSG boss this week following the sacking of Christophe Galtier.
PSG are also facing uncertainty around star player Kylian Mbappe, who has told the club he will not extend his contract beyond 2024.
-- Courtesy of BBC Sport