John told fans at his Born and Raised World Tour over the weekend (6 July) how Katy stood by his side while he recovered from throat surgery, explaining that she is "more incredible than I ever thought".
Singer-songwriter John was forced to postpone his tour last year after the throat condition granuloma, which put his career on temporary hiatus in 2011, had returned.
He said: "She was so patient as to even continue to get to know me and love me, and we would be on speakerphone and look at intermittent photos of each other."
John ended his speech by dedicating his final song 'A Face to Call Home' to Katy: "This is a long time coming for the both of us and I want to dedicate this next song to my Katy, who is my face to call home."
Last month, the couple sparked speculation that they had rekindled their romance after they were seen holding hands in New York. Prior to that, Katy, who split from ex-husband Russell Brand in December 2011, confessed that she was still "madly in love" with John.
Watch a fan video of John's dedication to Katy below: