The pair are known to millions as Nessa Jenkins and Bryn West - but this new show will see them appear as two brand new characters.
They'll play the title roles in a new half-hour comedy called Ray and Gaynor, the BBC has announced.
A teaser shares: "Meet Gaynor and Ray Davies from Cardiff – two fifty-something newlyweds, both married for a second time. Gaynor’s first marriage ended when she discovered her husband was unfaithful (multiple times); Ray’s first marriage ended because he was ‘impossible to live with’ (or so his ex-wife never tires of telling him). But now they’re both trying again.
"In this 35 minute special we join Ray and Gaynor on their honeymoon to the Scottish Highlands where they meet a variety of characters and situations.
"And having only met six months ago, there are many things – not all of them endearing – that this couple keeps discovering about each other, often begging the question have they done the right thing?"
Writer-creators David Peet and Ruth Jones said: "We’re delighted to watch Gaynor & Ray come to life on screen.
"Through them we get to see the male and female take on life and relationships as well as the nonsense in the day-to-day."
Gregor Sharp, Commissioning Editor for the BBC added: "Ruth and David’s portrait of the ups and downs of a new relationship is full of warmth, wit and wisdom and is brilliantly performed by the laugh out loud combination of Ruth and Rob, a match made in comedy heaven. We can’t wait for everyone to see it."
Gaynor & Ray was filmed on location in the North West Scottish Highlands and South Wales, with further casting and an air date to be announced.
The news comes after Ruth wouldn't rule out more episodes of Gavin & Stacey.
The show last aired a Christmas special in 2019 which peaked with more than 12 million viewers.
Ending on a cliffhanger as Ruth's Nessa character proposed to Smithy, played by James Corden, fans have been wanting another instalment ever since.
Ruth told The Sun newspaper: "I do say never say never, as while we did make it work that was after three years of trying to find time when we could sit down and write it.
"Obviously with the way it ends, there is room for more. It’s a shame we didn’t have more time when we were writing so we could have written more, then have it all ready to go."
For now you can watch Gavin & Stacey online via the BBC iPlayer here.