A boy is on his way to school one morning when he notices a red balloon fastened to a streetlight. He climbs up and takes possession of it, then continues on his walk past other people – who seemed surprisingly unaware that they were part of a movie. The balloon is nearly as large as the child, so naturally, he can’t take it on the bus; instead, he runs to school. On his way back home, he has some amusing encounters with those he meets in the rain along the streets of Paris before finally getting it inside, but his grandmother immediately lets it go out the window. It could be interpreted as a symbol of something, but the balloon is determined not to leave its new owner, even when exposed to the weather. It acts like an animal companion, responding to commands and joining in games; classmates attempt to grab it, it causes him some minor issues with the church, and it encounters another balloon—a blue one. The balloon is even stolen at one point, and they are separated, leading to what appears to be a sorrowful ending. Or perhaps not? It's quite ingenious how the balloon is moved around – it almost seems as if it’s being controlled remotely! There’s also something captivating and delightful about the uncomplicated nature of this brief film. The soundtrack is upbeat and playful, reminiscent of Disney films, and Pascal Lamorisse is undeniably endearing in his role as the easily satisfied boy.

Source on TMDB