The Tottenham Hotspur graduate issued a statement on Tuesday confirming that he has walked away from the game on medical advice due to a head injury that he suffered more than a year ago.
Mason, who signed for Hull a year-and-a-half ago, fractured his skull during a collision of heads with Chelsea defender Gary Cahill in January 2017.
The midfielder had hoped to return in 2018, but the risks of playing competitively are too high.
On Twitter, Chelsea posted a message to the footballer, saying: "Everybody at Chelsea Football Club sends our best wishes to Ryan Mason following his retirement. Good luck in whatever you choose to do next, Ryan."
The midfielder earned one England cap in his career.