The half-hour special has the working title of A Winter's Tale From Shaun The Sheep.
The BBC explains: "Shaun's seasonal excitement turns to dismay when a farmhouse raid to get bigger stockings for the Flock inadvertently leads to Timmy going missing.
"Can Shaun get Timmy back before he becomes someone else's present? Prepare for a 'Santastic' adventure as everyone learns the true value of Christmas!"
To accompany the announcement, production company Aardman have released an image featuring Shaun, Timmy and his teddy making snow angels.
Sue Deeks from the BBC says: "Aardman lovingly produce stories with warmth, personality and humour, so we are truly delighted that, following the huge success of The Farmer's Llamas [in 2015], the next project in our continuing relationship is another wonderful Shaun The Sheep special."
Sean Clarke from Aardman comments: "Aardman films have come to be synonymous with the festive period, which is a real honour. We're delighted to be continuing this tradition with a Shaun The Sheep seasonal special that will premiere on the BBC for Christmas 2021."
The half hour special, which is written by Giles Pilbrow and Mark Burton, will start filming in late 2020. As it is a stop-motion production with each frame individually photographed, it will be in production for some time.
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