A few people have mentioned Apollo 11 but I prefer (and my favorite documentary of all time is) For All Mankind (1989). They’re similar, iirc they share a lot of the same footage, but For All Mankind gives you a great sense of what it was like for those early astronauts to take that trip to the Moon. It has all the best footage of the moon we have ever taken. For All Mankind is a must, but both are worth a watch if you’re a space fan.

Crumb is also pretty good. It’s about an offbeat artist and gives you the look into the mind of someone that wouldn’t normally be in the spot light.