Line 3 (French pronunciation: [liɲᵊ tʁwa]) is one of the sixteen lines of the Paris Métro rapid transit system in Paris, France. Connecting Pont de Levallois - Bécon station in the near western suburbs to Gallieni in the east, the location of Paris' international bus station. After opening as the third line in 1904, the line was the subject of a number of extensions, with a major restructuring occurring in the eastern section in 1971, with an extension to Gallieni and the conversion of the original terminal branch to Line 3bis.

With a length of 11.7 km (7 mi), Line 3 crosses Paris from west to east completely on the Right Bank, serving the residential areas of the 17th arrondissement, Saint-Lazare station, important stores and shopping centres, the area around the Place de l'Opéra, and the east of the city. In 2004, it carried 87.6 million passengers, making it the ninth busiest line of the Métro.