The South Korea international has completed a €40M transfer move to Madrid after growing frustrated as a back up player at PSG across the last three seasons in France.
His switch to Madrid comes as his third spell in LaLiga - after previous stints at Valencia and Mallorca (six league goals scored at the latter before moving to Paris) - with Morten Hjulmand and Alex Grimaldo also joining in the off season.
These new arrivals are balanced the exit of a club icon, following Antoine Griezmann's decision to leave as Los Rojiblancos' record goal scorer, to join MLS team Orlando City on a free transfer.
Ahead of the changing of the guard in Madrid, Griezmann posted his backing to Kang-in Lee on social media as he prepares for a club debut under Diego Simeone.
Atletico Madrid kick off their preseason campaign against neighbours Getafe on July 24, followed by August clashes with Manchester United, Manchester City and Marseille, before the start of 2026/27 La Liga at home to Malaga on August 19.