Chemin de fer de Petite Ceinture, Circular railway line in Paris, France.

The 32-kilometer (20-mile) ring route circles central Paris through various neighborhoods, running along tunnels, viaducts, and ground-level tracks. Multiple former stations dot the line, their 19th-century architecture still visible beneath layers of vegetation. Some segments have been converted into green corridors, while others remain fenced off or continue serving freight operations.

Construction began in 1852 under Napoleon III to link the city's terminal stations, and the line opened in sections from 1852 to 1869. Passenger service started on 14 July 1862, and traffic peaked at 38 million riders during the 1900 Universal Exposition. Passenger service closed on 23 July 1934, replaced by the PC bus line, while freight continued until the 1990s.

Opened to passengers on 14 July 1862, the line gave workers a cheap circular service through the outer arrondissements where Haussmann's works had pushed them. Its name, "Little Belt", echoes the ring of fortifications it ran inside. Since 2007, with SNCF's agreement, the City of Paris has turned some stretches into temporary green corridors, and the line now hosts occasional cultural events.

Several sections of the former track are now accessible as public pathways for walking or cycling through different districts. Access points exist in the 12th, 15th, 16th, and 18th arrondissements, with some portions open seasonally or during scheduled times. Other segments remain closed to the public or continue serving freight trains.

The infrastructure includes 12 tunnels and 24 bridges, with abandoned stations gradually overtaken by wild vegetation since closure. In the 1990s, portions served as filming locations for French cinema. The former Auteuil station now houses a restaurant, while other station buildings have been converted into private residences or artist studios.