The day starts with a big parade down the most famous avenue in Paris, the Champs-Élysées. There are marching bands, music, flag-waving and a fly-past of planes that trail blue, white and red smoke - the colours of the French flag. Children come out with their families to watch.
In small towns and villages across France, the day is more relaxed. Many places hold a bal du 14 juillet - a big open-air dance party in the village square the night before. The local fire station often holds a 'firemen's ball' too - they open up their courtyard and turn it into a dance floor.
Then come the fireworks. Every town puts on its own show, but the most famous one is in Paris. Thousands of fireworks light up the sky right around the Eiffel Tower, while a huge orchestra plays music to match the explosions. Around half a million people watch the Paris show in person.
The French flag has three vertical stripes: blue, white and red - the famous tricolore. On Bastille Day, you'll see those three colours everywhere - on bunting, on flags hanging from windows, on people's faces, on cakes, and high in the sky as the planes fly past.