The Fox is one of the minor antagonists of the Shaun The Sheep series. He's a fox who lives in a tree stub just outside Mossy Bottom Farm, and repeatedly tries to steal one or more of the animals on the farm. Because of his stealing behavior, he's hated/opposed by the Flock, Bitzer and the Farmer.
The Fox did kidnapped The Rooster to eats him, which it will prevents The Farmer and most of the sleeping farm animals from waking up. Shaun and Bitzer saved The Rooster, so he can does his usual morning routine of waking the rest of the farm up, including The Farmer who chases after The Fox.
Shirley was once in love with the Fox when he was dressed up as a male sheep (in the episode Foxy Laddie), but his plans to abduct Timmy was spoiled by the Flock (Shaun and Bitzer in particular), and at the end, the Fox was beaten up by a very unfriendly Shirley.