Gorgo

Greedy sailors capture a giant lizard off the coast of Ireland and sell it to a London circus, inciting the wrath of the creature's much-larger mother.

Gorgo is a 1961 horror sci-fi movie directed by Eugène Lourié, starring Christopher Rhodes, William Sylvester, Bill Travers. It holds an IMDb rating of 5.6/10 from 4,892 votes and runs 1h 18m.