The pop producer and songwriter from the late 90s through today. If you’ve listened to the radio anytime since, say, 1998 or so, you’ve heard something he’s written or produced (or likely both). He’s written 22 number-one hits, the third most all time behind Paul McCartney and John Lennon. See his full songwriting and production credits here and BuzzFeed’s list of his 18 greatest songs here.
Max Martin's first song DJ Got Us Fallin’ In Love released on Thu Jan 01 1970.