Digby, the Biggest Dog in the World is a 1973 British children's fantasy-adventure comedy 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. The production included composer Edwin Astley and cinematographer Harry Waxman. The film was based on the 1960 novel The Biggest Dog in the World by Ted Key.

Plot

Accident-prone Jeff works at a NATO research facility as an animal behaviourist. He steals a tiny amount of Project X, but an Old English Sheepdog accidentally drinks it. X is a liquid growth formula (a form of experimental fertilizer) and Digby expands to gigantic proportions.