Ratatouille is a traditional French dish that is featured in the titular Disney/Pixar film. Ratatouille.
Ratatouille is the dish which Remy and the rat clan made to food critic, Anton Ego, who luckily happened to have loved the dish in his early childhood, and happily ate the dish at Gusteau's. Soon after people realized that rats were present in the kitchen, the restaurant was closed due to infestation. Ego also lost his job and credibility as a restaurant critic, and was instead made an investor to Remy's own personal restaurant, La Ratatouille, where he would almost always ask for this dish. The name of the dish was first spoken in the movie by Linguini whilst drunk.
The version of the Ratatouille dish in the film was actually the version Confit byaldi, to make the food look tasty and delicious, compared to the traditional version. Although the traditional version appeared shortly in a flashback scene.