Shore last fought against Youssef Zalal in November, suffering a second-round submission defeat.
“For the entirety of my 20’s, fighting and training was my life and sole focus, however, the last few weeks/months have shown this is no longer the case,” he added.
“And I always promised myself when I was mentality checked out I would retire from the sport rather than the sport retire me. Injures have caught up with me after a lifetime in the sport.
“I’m leaving with my mental [health] in check, good health, financially stable and am fully ready to move on to the future.”
In his lengthy post, Shore thanked the UFC, his family, friends, coaches and gym.
“What a journey,” he added. “For once, I can finally say I’m proud of what I’ve achieved and always did my best.
“Hopefully, when people think of Welsh MMA they’ll always think of Tank Shore. Big love to you all. Tank out.”