Quoth IMDB on Mel Brooks’s Silent Movie:
So what were the runners-up in this category? (Let’s count feature-length films only, as I’m sure there have been many shorts with no spoken lines.) The only candidate that comes to mind is Charlie Chaplin’s 1936 Modern Times, a sort of bridge between his silent and sound movies. In that film voices are heard only from machines and electronic devices (phonographs, radios, intercoms, etc.); when a live character speaks, title cards are used.
It’s been a long while since I saw Ballad of Gregorio Cortez but I don’t think it had much dialogue at all.
There’s also a movie whose name I can’t remember which is all about a guy running away from cannibals/headhunters who have cooked his companions and want to get him. Drums, but, again, not a lot of dialogue.
In Luc Besson’s first film Le Dernier Combat, there is not a single word of spoken dialogue.
I am a Besson fan, so my opinion is admittedly biased, but this is an excellent film, and tells quite an involved story, all without any spoken words. No captioning, either.
I guess Guinness overlooks it because it’s not an American movie.
What about Koyaanisqatsi? I don’t think that had any spoken words at all … or does the record imply fewest spoken lines greater than zero?
In fact, all 3 movies in the 'sqatsi series have no spoken words… but they are more like 90 minute montages than a serious attempt at telling a story.
(They do rock tho… I own all 3!)
Speaking of montages, I just remembered another one: Baraka (1992). I’m pretty sure that has no dialogue.
One Million Years BC no dialogue at all, just a bit of narration.
You don’t count grunts as dialogue?
If that’s true, I nominate every Sylvester Stallone movie ever made.
No, it’s because Le Dernier Combat has two lines of (whispered) dialog as opposed to one line in Silent Movie.
Quest for fire was pretty sparse in the words.
I am not a fan/expert as far as the genre goes, but I am positive there are a lot of feature-length porno films out there that would quallify. 
No, seriously!
Didn’t Luise Rainer set some sort of record for winning an Academy Award in The Good Earth with a tiny number of words of dialogue?
When I first saw The Thief (1952) on Matinee Theater or Films of the Fabulous Fifties or whatever TV show it was that had old film noir and detective and spy movies, I wasn’t expecting anything special or weird. There is a soundtrack and all sorts of incidental sounds like clocks ticking and traffic and phones ringing. But no dialog. Nothing spoken.
Ray Milland gets in all sorts of situations where you just know he has to say something – but he never does.
Read the link for some reactions to this “conceit” but if you give it a chance I think you would be favorably impressed. Now that you know there’s no dialog, it can’t hit you the way it did me, but it’s still fun to experience.
Hell in the Pacific with Lee Marvin and Toshiro Mifune had no real dialogue since dialogue by definition is two people talking to one another. Since the two characters (and two actors for that matter ) did not speak one another’s language, there was not true dialogue.
Jeramiah Johnson with Robert Redford had a limited amount of communication also.
Less dialogue than average, maybe, but it had some, like the scene of the preacher urging Johnson to track down some lost settlers.
In fact, here are a bunch of quotes from the movie.
" You don’t coun’t grunts as dialogue?"
Man, that was a great film, can anybody remember the title? The main actor’s name is also on the tip of my tongue, but won’t come out either.
It did have a couple scenes where he met kid and they spoke alittle, IIRC. I love the end where after being pursued for days on end, he finally ran towards an army fort. In the middle of the field in front, he looked back and the natives were just standing there looking at him. Finally, the leader waved in a salute to his fortitude.
Somebody tell me the title, please, want to get it from Netflix!
It’s been a while since I saw it, but as memory serves Jerry Lewis’s The Bellboy has very little dialogue, just lots of slapstick comedy with enough dialogue to set it up. Jerry plays the title character and also plays himself, and IIRC his only lines are as himself until the final minute of the movie.