Kai Harley Wagner (born 15 February 1997) is a German professional footballer who plays as a left-back for the Philadelphia Union of Major League Soccer.

Ahead of the 2015–16 season, Wagner signed his first professional contract at 18 years old with SSV Ulm competing in the Oberliga Baden-Württemberg, the fifth tier of German football.

[2] Wagner made 32 appearances and scored one goal, helping earn SSV Ulm the championship title and promotion to the fourth tier Regionalliga.

[2] In summer of 2016, Wagner secured a transfer to Schalke 04 II competing in the Regionalliga West, the fourth tier of German football.

The violation happened on 28 October 2023, during a match against New England Revolution when Wagner called an opposing forward, Bobby Wood, a slur considered racist towards Asian people.