Picnic on the Grass (French: Le Déjeuner sur l'herbe) is a 1959 French comedy film written and directed by Jean Renoir, starring Paul Meurisse, Fernand Sardou and Catherine Rouvel. It is known in the United Kingdom by its original title or in translation as Lunch on the Grass. A satire on contemporary science and politics, it revolves around a prominent biologist and politician who wants to replace sex with artificial insemination, but begins to reconsider when a picnic he organizes is interrupted by the forces of nature. The film brings up issues of modernity, human reproduction, youth and European integration. It ridicules rationalist idealism and celebrates a type of materialism it associates with classical mythology and ancient Greek philosophy.

The title is taken from the painting Le Déjeuner sur l'herbe by Édouard Manet. The female lead in Picnic on the Grass was the first major role for Rouvel, who due to an unusual contract would not appear in another film until 1963. Filming took place around Renoir's childhood home in Provence, and inspiration came from the impressionist paintings of his father, Pierre-Auguste Renoir. The filming technique was influenced by live television and involved multiple cameras and direct audio recording.

The press reviews were generally positive and described the film as charming and beautiful. Negative response came from the political left, where critics disapproved of the film's treatment of progress and depiction of a European superstate; the subject of European unification was topical and sensitive due to the creation of the European Economic Community in 1957. In spite of the generally good reviews, the film was a commercial failure, and has attracted little attention from general audiences over the years. Some modern critics have seen its implicit critiques of technocracy and dogged rationalism as both prophetic and of increasing relevance to today's world.