Monte Carlo, town (1982 pop. 13,150), principality of Monaco, on the Mediterranean Sea and the French Riviera. It is a tourist center noted for its world-famous gambling casino (built 1858) and for its scenery, fine villas, and luxurious hotels. In 1954 the concession came under the control of the Greek shipping magnate Aristotle Onassis but has since been returned to the Monaco government. Among the sporting events of the town are the famous Monte Carlo car rally, the Monaco Grand Prix, and the Monte Carlo Open tennis tournament.