Gordon, who joined Newcastle United from Everton in January 2023, spent three and a half seasons at St James' Park and scored 59 goals across all competitions. He posted the letter on his social media channels alongside a video reel of his goals and moments in a black-and-white shirt.
The full text read:
"To Newcastle,
"Three and a half seasons have flown by, and it feels like I've been here all my life. I arrived as a young boy who had just left home and didn't know what was to come, but from the very first day I knew I had come to the right place. I joined Newcastle because I felt my ambitions matched those of the club, the staff and the players, and from my first session I knew this was the place I needed to be.
"To my teammates, staff and coaching staff, I'm so thankful and grateful that I got to share every day with you all. I wouldn't be the person or player I am without all of you pushing me each day and the special relationships I have been able to forge during my time here. The culture at Newcastle is one of the best in terms of discipline, hard work and simply being surrounded by good people. In every training session and in every match with the Newcastle shirt, I knew my team had my back, and I never took that for granted. It's very rare to find people who want your success as much as you do yourself, and I felt that every day.
"To the fans: I arrived in difficult circumstances but you believed in me from day one, and I was determined to prove you right. When I first heard my song at Chelsea I knew I had to give you something to cheer about, and I hope you know I gave absolutely everything for you and for the club. Some of the nights we shared at St James' Park are unforgettable and created some of the greatest atmospheres I have ever experienced. I hope you achieve the success you deserve for the incredible commitment you show in supporting Newcastle, and it has been a privilege to play in front of you, both at home and away.
"These years have been very successful both for the club and for me personally — we qualified for the Champions League in two of the three seasons after being away from the competition for so long, and we won the club's first trophy in 60 years. I am proud to have been part of this period in the club's history.
"I'm going to miss everything about Newcastle, and these truly have been the best years of my life. Inside and outside the pitch, I've created memories I will cherish forever. I'm no longer a Newcastle player, but I will always be a fan, and I'll keep supporting the team from a distance.
"Thank you for everything, Anthony."
Manager Eddie Howe spoke directly about the departure: "While we are disappointed to lose Anthony, we understand this is a great opportunity for him. I'm confident he will go on to be a success, both with Barcelona and the national team at this year's World Cup."