Back when I wrote an article about my 95 for Petrolicious, I commented that the Saab 95 was a hatchback before people knew what a hatchback was, so they called it a wagon.
Some people claim the Renault 4 was the first hatchback, but if it is actually hatchback, then surely, the Saab 95 would have to be a hatchback, and came first.
Others believe the Renault 16 or the Simca 1100 are the real first true hatchbacks. But I think, in the Saab 95's favor is its three door body and small overall size. The 95 is basically “supermini” sized, before that became a thing. It’s true, the 95 has D pillars, but the C pillars are essentially vestigial, and only there so the back windows can hinge open.
The strongest argument against the 95 being a hatchback is probably the rear facing jumpseat in the back, which is almost definitively a station wagon feature. And yet, the top hinged rear door... was almost unique among 1950's cars. Citroen’s Traction Commerciale had one... and that was about it until the 95 came along.