The Christchurch native - who initially shot to prominence as part of the all-conquering New Zealand U20 side that claimed World Rugby U20 Championship gold in 2017 - has become an integral part of the Glasgow Warriors squad since arriving at Scotstoun in November 2021, a series of impressive performances endearing him to the Warrior Nation.
His debut came in victory over the Dragons at Scotstoun in December 2021, becoming the 338th player to pull on a Glasgow Warriors jersey in the professional era.
Equally as comfortable on the wing as he is at full-back, McKay has touched down for eight tries in his 27 appearances in all competitions to date, most recently in the 50-8 victory over Zebre Parma at Scotstoun in March.
The 25-year-old has also represented Canterbury with distinction in the Mitre10 Cup, crossing for 11 tries in 11 outings for the men in red and black in 2019.
"In the end it was a really easy decision [to re-sign]," McKay told glasgowwarriors.org.
"I absolutely love the direction in which this club is travelling, and when I sat down and thought about what I want to do over the next couple of years it really aligns with the vision of everyone here at Scotstoun.
"We've got the freedom to play and have a go, and playing in the back three that's exactly what you want to hear - you want to do your bit for the team and help the group excel. It certainly suits the style of rugby I love to play and I'm really excited for what comes next.
"Glasgow's an awesome city to be a part of, too - when I initially moved over from New Zealand, I didn't really know what to expect, but I've absolutely loved getting settled into the city. We live near a lot of the boys and it's a really good environment in which to live and work.
"First and foremost I want to get back fully fit and firing, so the focus for me now is to get my foot right and then get ready to attack next season. I can't wait."
Head Coach Franco Smith added: "We're pleased that Josh has committed his future to us for the next couple of seasons.
"He's a model professional that brings a great attitude and desire to improve to every training session, and his ability to play on both the wing and at full-back is a real asset to us as a squad.
"He comes to Scotstoun each day with a real drive to be the best version of himself that he can be and we look forward to continuing to work with him over the coming seasons."