Wikipedia’s list of Apocalyptic films begins with a film called End of the World from 1916, and another film, also called End of the World, from 1931. The third one on the list is the one I would vote for as the oldest truly post-apocalyptic film, Deluge from 1933.
When I say “truly post-apocalyptic”, I mean that it doesn’t just portray a global catastrophe, like the two End of the World films that came before, but it actually focuses on the aftermath of the event, and tells the story of the survivors.
Deluge is based on a novel of the same name by S. Fowler Wright written in 1928.
The film begins with scientists warning of massive impending natural disasters. The first 20 minutes or so are filled with amazing scenes of panicked citizens trying to flee, and cities being wiped out by massive earthquakes and tsunami.
Usually when I watch a movie, I’m also browsing the web in another window, but for Deluge the opening scenes were so good I didn’t want to look away. I mean, yes, you can plainly tell that you’re looking at models, but considering it was made almost 90 years ago, they did a great job. The destruction of New York City was so well done that it was later recreated in 2004’s The Day After Tomorrow.
After the catastrophe subsides, the pace of the film slows down a bit, but it’s no less interesting. Fans of the genre will recognize what we now consider to be tropes, like gangs of marauders stealing food and women, and survivors fighting over scavenged supplies.
I enjoyed the film just as a disaster and survival flick, but being the first is always important, so given it’s vintage status, I would bump this one up a bit on your “to watch” list.
One interesting note about the film is that it was considered lost until an Italian dub was re-discovered in 1981. But it wasn’t until 2016 when a 35mm print of the English version turned up in an archive that it was restored and released on disc.