The midfielder is leaving this summer as his contract expires at the end of the month.
"After eight incredible years, my journey with Newcastle has come to an end and before I begin to prepare for an exciting new challenge at my new club - I wanted to take a moment to express my heartfelt gratitude to everyone who made my time here so special.
"To the fans, your unwavering support has and always will mean the world to me.
"From the elation of scoring the winner against Burton Albion as we chased promotion, to a personal highlight of mine, seeing out a 1-0 win over Man United to help secure our Premier League status in 2018 - these moments, where we battled and triumphed together at St. James' Park, will always hold a special place in my heart.
"Newcastle United is filled with extraordinary people who made my time here so special. There's no doubt that I'm leaving this club with friends for life.
"To the manager, coaches, my teammates and all the amazing staff at the club, it was a privilege to be part of such a talented, dedicated and ambitious team. Your hard work and friendship made every day a joy, and I am proud to have worked alongside you all.
"There's no doubt in my mind that this club will continue to grow from strength to strength over the coming seasons and I will be watching proudly from afar as a fan.
"Finally, I want to end by thanking every single Newcastle United supporter - you are the beating heart of this one-of-a-kind club and without you, none of this would have been possible.
"Matt Ritchie"