The Puffing Billy Railway is a 2 ft 6 in narrow gauge heritage railway in the southern foothills of the Dandenong Ranges in Melbourne, Australia. The railway was one of the five narrow gauge lines of the Victorian Railways which opened around the beginning of the 20th century. It is close to the city of Melbourne and is one of the most popular steam heritage railways in the world, attracting tourists from Australia and overseas. The railway aims to preserve and restore the line as near as possible to how it was in the first three decades of its existence, but with particular emphasis on the early 1920s.

2 ft 6 in gauge railways are narrow gauge railways with track gauge of 2 ft 6 in. This type of rail was promoted especially in the colonies of the British Empire during the second half of the nineteenth century by Thomas Hall and Everard Calthrop.