The Nilgiri Mountain Railway is a 1,000 mm metre gauge railway in Tamil Nadu, India, built by the British in 1908. The railway is operated by the Southern Railway and is the only rack railway in India.
The railway relies on its fleet of steam locomotives. NMR switched to diesel locomotives on the section between Coonoor and Udhagamandalam. Local people and visitors led a campaign to return to steam locomotives in this section.
In July 2005, UNESCO added the Nilgiri Mountain Railway as an extension to the World Heritage Site of Darjeeling Himalayan Railway. The site then became known as Mountain Railways of India.