Even NBA MVPs can't get enough of Harry Styles ... 'cause Giannis Antetokounmpo was among thousands of super fans hitting up the singer's concert in Milwaukee on Wednesday -- and he was loving every second of it!!

The concert took place at the Fiserv Forum, where Giannis routinely dunks on his opponents night in and night out ... but this time, #34 was there to catch some sounds and enjoy the vibe from the superstar musician.