The two pop superstars were believed to have fallen out after Katy took three of Taylor's backing dancers for her 'California Dreams' world tour before her 'Red Tour' had finished in 2013.
The pair then traded verbal blows on Taylor's track 'Bad Blood' and Katy's song 'Swish Swish' but now they have put their feud behind them.
Taylor, 29, has opened up about their reconciliation for the first time and revealed they have been close again since Katy sent an actual olive branch to her as a sign of peace on her 'Reputation' tour last year, and how she feels "lighter about life" again now they have ended their feud.
Speaking to Capital's Rob Howard - in for Roman Kemp, Vick Hope & Sonny Jay who are on holiday this week - on Capital Breakfast, Taylor spilled: "She and I have really been on good terms for a while.
"She sent me a really nice note and an olive branch to the - like an actual olive branch - to my tour when it started, the 'Reputation' stadium tour, a while ago. "From that point on we've been on good terms.
"Then we saw each other at a party and walked up to each other and hugged it out and talked about things, and then we saw each other again and hung out at another party and it was just like something felt so much lighter about my life when things became really good between us.
"And, you know, she and I have been fine for a while and really on good terms but we didn't know if we were ever gonna really tell people about it.
"We wanted to make sure that was solid between us before we ever made the public aware."
The 'Shake It Off' hitmaker breaking her silence on their reunion comes after the pair dressed as a hamburger and French fries in the new video for Taylor's single 'You Need To Calm Down'.
Taylor unveiled the promo on Monday (17.06.19) and in it Katy, 34, appears dressed as a giant burger in a food fight scene towards the end of the video and she spots Taylor in a French fries outfit and the pair come together for a cuddle.
Both singers shared stills of the moment on their Instagram accounts, with the 'ME!' hitmaker captioning the post: "Happy meal (sic)"
Katy wrote: "This meal is BEEF-free (sic)"
Hear Taylor Swift's interview in full on Capital Breakfast tomorrow (Tuesday 18th June). Tune into Capital Breakfast, week days from 6am - 10am across the UK.