The 45-year-old presenter has been fronting the gameshow ever since previous host Anne Robinson stepped down from the role last September.
Announcing the news on Steph's Packed Lunch, Murray said: “It’s a career dream to be named as permanent anchor of one of television’s most iconic programmes."
Read more: Everyone who has hosted Countdown
He added: “I have been a fan since day one, been part of the family for over a decade, appearing on Dictionary Corner, and now I get the honour of guiding it into a fifth decade."
Murray also stressed that he wants to see the long-running show continue to see its audience improve: “However, I don’t just want Countdown to survive, I want it to thrive.
"During my caretaker stint we’ve seen more people tune back in, with close to a million (900,000) watching the series final in December, and I want that to just be the beginning."
He also urged people to give the show a go if they had never seen it or not watched in years.
Murray is the seventh permanent presenter of the show, which premiered in 1982. Countdown was originally presented by Richard Whiteley who hosted the show for 22 years.
Countdown has since been presented by Des Lynam, Des O'Connor, Jeff Stelling, Nick Hewer and Anne Robinson.
Read more: Lorraine urges Vorderman to host Countdown
Murray is best known for his sports presenting having previously fronted Eurosport's coverage of snooker and the Football League's highlights show on Channel 5 and Quest.
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