I’m surprised only a handful of people have mentioned Ghibli movies. For me it was Nausicaa of the Valley of the Wind, it’s probably one of the first movies I remember watching in general. Still my favorite Ghibli movie and I must have watched it dozens of times as a kid.
The source material for it is a manga by Miyazaki himself and it’s much longer and deeper (the movie only covers about 1.5 out of 7 volumes, and changes a lot of details). Highly recommended.