Jardin d'Acclimatation railway, Narrow-gauge railway in Bois de Boulogne, France.

The Jardin d'Acclimatation railway is a 500 mm minimum-gauge line in the Bois de Boulogne, running 800 metres from Porte Maillot to the Jardin d'Acclimatation. Its trains are pulled by small steam-outline locomotives, seven of them built by Renault in 1960, each 3.05 m long, 1.20 m wide and weighing five tonnes. The carriages date from the 1910s, fitted with a light roof in the 1950s.

The line opened in 1878 when Paul Decauville, refused permission for a Trocadéro–École militaire route, installed a 1,500-metre circular 500 mm track inside the Jardin d'acclimatation, carrying up to 3,000 passengers on some Sundays at 15 km/h before being quickly dismantled. In 1880 another company laid a modified line to Porte Maillot, operated with pony-hauled tramway cars until tractors took over around 1910. The line was shortened at both ends around 1930, removing the section inside the garden and moving the terminus along the route de la Porte-des-Sablons.

The line's nickname, Le Petit Train, comes from its early years: ponies pulled open carriages with eight seats, passengers sitting back to back on longitudinal benches. In 1901 American newspapers described the locomotive as resembling a cross between a great Chinese dragon and a sea serpent, its carriages forming the joints of the body.

The line runs every day of the year during the garden's opening hours, linking Porte Maillot to the Jardin d'Acclimatation over 800 metres. Trains follow a slightly different route in each direction through the Bois de Boulogne, and the curves have a minimum radius of eight to fifteen metres.

The line's original 1878 layout was a 1,500-metre circular track inside the garden, with trains running at a maximum of 15 km/h and carrying up to 3,000 passengers on some Sundays. The network was dismantled soon afterwards for reasons the sources do not record.