Paris's former Chemin de fer de Petite Ceinture ('small(er) belt railway'), also colloquially known as La Petite Ceinture, was a circular railway built as a means to supply the city's fortification walls, and as a means of transporting merchandise and passengers between Paris' major rail-company stations. Beginning as two distinct 'Ceinture Syndicate' freight and 'Paris-Auteuil' passenger lines from 1851, these lines formed an arc that surrounded the northern two thirds of Paris, an arc that would become a full circle of rail around the capital when its third Ceinture Rive Gauche section was built in 1867.

Although the Syndicate-owned portion of the line was freight-only in its first years, after the creation of a passenger service from 1862, the Chemin de fer de Ceinture became Paris's first metro-like urban transport, and even more so after the 'Ceinture Rive Gauche' passenger-and-freight section began. The line's passenger service was a popular means of public transport until its 1900 Universal Exposition peak-traffic year.

Paris's first Metro line opened that year: from then, the numbers of those using the Petite Ceinture passenger service dropped steadily until its closure in 1934. Although maintained as a freight line, even this use of the Petite Ceinture had come to a practical standstill by the 1980s.

Since then, sections of the Petite Ceinture's trenches and infrastructure have been recuperated and renovated for the inter-urban RER C passenger transport service, some of its former stations have been sold to local commerce and services. The future of the remaining stretches of Petite Ceinture has always been, and still is, the source of much debate.