Addysen Tully is an unseen character in Game of Thrones. She is already long deceased by the time the series begins and is therefore not expected to appear. She is the firstborn child of Lord Ambrose Tully and his wife, and was the older sister of Hoster and Brynden "The Blackfish" Tully.
She was killed during House Keller's attack on Riverrun after House Tully refused to ally with the Kellers by betrothing Addysen to Tylan Keller.