Director Bob Rafelson fulfilled a lifelong dream when he finally received backing to complete Mountains of the Moon. The film recreates the exploratory adventures of 19th century visionaries Sir Richard Burton (Patrick Bergin) and John Henning Speke (Iain Glen). The heart of the film is the effort by Burton and Speke to discover the true source of the Nile river. This occurs well into the film, after several torturous scenes involving the injuries sustained by the protagonists during other expeditions and their growing friendship (which, the film intimates, goes far beyond friendship). Rafaelson's fascination with this story, and his insistence upon painstaking historical accuracy, unfortunately compromises his ability to make an interesting film. There are so many starts and stops during the first half that we sincerely hope Burton and Speke will chuck it all and set up a pub in Bristol or something. What saves Mountains of the Moon is the rapport between its stars and the brilliant, epic-like cinematography of Roger Deakins.
~ Hal Erickson, All Movie Guide