Digby, the Biggest Dog in the World is a 1973 British children's film starring Jim Dale, and directed by Joseph McGrath. A large supporting cast of British movie stalwarts includes Spike Milligan, Angela Douglas, Norman Rossington, Milo O'Shea, Dinsdale Landen and Victor Spinetti. Other notable crew include composer Edwin Astley and cinematographer Harry Waxman.
It was the third programme shown on Central Television and the second programme from TVS Television.
The story is about a sheepdog who accidentally drinks a liquid growth formula and swells up to enormous proportions. Two criminals steal Digby, the sheepdog, and sell him to a circus. Digby, however, escapes by breaking his chains and running at will across the countryside of the United Kingdom. The boy who owned Digby and the scientist who worked on the growth formula realise that Digby is constantly increasing in size, and will cause massive damage unless something is done; in which the scientist finds he may have created a chemical that might reverse the growth formula. The British military, however, is attempting to solve the problem of the oversized sheepdog in their own way, by use of weaponry.