The Kalka–Shimla railway is a 2 ft 6 in narrow-gauge railway in North India which traverses a mostly mountainous route from Kalka to Shimla. It is known for dramatic views of the hills and surrounding villages. The railway was built under the direction of Herbert Septimus Harington between 1898 and 1903 to connect Shimla, the summer capital of India during the British Raj, with the rest of the Indian rail system.
Its early locomotives were manufactured by Sharp, Stewart and Company. Larger locomotives were introduced, which were manufactured by the Hunslet Engine Company. Diesel and diesel-hydraulic locomotives began operation in 1955 and 1970, respectively.
On 8 July 2008, UNESCO added the Kalka–Shimla railway to the mountain railways of India World Heritage Site.