École polytechnique, also known as Polytechnique or l'X [liks], is a grande école university located in Palaiseau, France. It specializes in science and engineering and is a founding member of the Polytechnic Institute of Paris.

The school was founded in 1794 by mathematician Gaspard Monge during the French Revolution and was militarized under Napoleon I in 1804. It is still supervised by the French Ministry of Armed Forces. Originally located in the Latin Quarter in central Paris, the institution moved to Palaiseau in 1976, in the Paris-Saclay technology cluster.

Polytechnique’s historic engineering graduate program has a highly selective admission process consisting of written and oral examinations, following classes préparatoires or a bachelor’s degree. French engineering students undergo initial military training and have the status of paid officer cadets. The school has also been awarding doctorates since 1985, masters since 2005 and bachelors since 2017. Most Polytechnique graduates go on to become top executives in companies, senior civil servants, military officers, or researchers.

Its alumni include three Nobel Prize winners, a Fields Medalist, three Presidents of France and many CEOs of French and international companies. Among them are mathematicians such as Cauchy, Coriolis, Henri Poincaré, Laurent Schwartz and Benoît Mandelbrot, physicists such as Becquerel, Carnot, Ampère and Fresnel, and economists Maurice Allais and Jean Tirole. French Marshals Joffre, Foch, Fayolle and Maunoury all graduated from Polytechnique.

Although Polytechnique enjoys great prestige in French higher education because of its selectivity and academic excellence, it has been criticized as elitist and technocratic. In the popular imagination, the school is associated with symbols such as the student uniform and the bicorne.