The Groudle Glen Railway is a 2 ft (610 mm) narrow gauge railway near Onchan in the Isle of Man, on the boundary of Onchan and Lonan, which is owned and operated by a small group of enthusiastic volunteers and operates on summer Sundays; May to September and Wednesday evenings in July and August along with a number of annual special events.

The line was built in the late Victorian era to cater for a new demand for transport down Groudle Glen after the opening of the Manx Electric Railway.

The 2 ft (610 mm) narrow gauge line ran from the upper part of the glen, Lhen Coan, to the zoo at Sea Lion Rocks.

The final two seasons were known as the "fairground era" as the stock was painted in loud colours with blue and red dominating, and fairground-style lettering and lining applied to the locomotive.

In 1982, the Isle of Man Steam Railway Supporters' Association launched a plan to restore the line, and work began clearing twenty years worth of undergrowth covering the trackbed.

The complete railway was officially re-opened on 23 May 1986 by Carolyn Rawson as part of the Manx Heritage Year and a tree planted to mark the event in Lhen Coan station.

Planning permission was granted in 1999 for the volunteers to erect a replacement station building at Sea Lion Rocks, and by summer 2000 work was well in hand.

Plans were well in hand to rebuild the souvenir shop at Lhen Coan in a style similar to the distinctive station canopy, and in late 2008 the previous incarnation was dismantled in readiness for the erection of the new, pre-fabricated version on the same site.

A mock signal box was also completed to cover the side of the volunteers' mess room, and by December 2008 work was in hand to close the shop for good after the Santa Trains.

In 2010 an appeal was launched to raise the £60,000 required to extend the Sea Lion Rocks Tea Rooms to provide toilet facilities, a power supply and improved patio area.

This was completed in time for the Easter 2012 services, and was re-opened by Allan Bell MHK, the island's Chief Minister, in May 2012 to mark the 30th anniversary of the railway's restoration.

During the 2012 season planning permission was granted to enlarge the platform area at Lhen Coan station and to construct a new utility building to replace the time-expired tea hut, which was demolished after Christmas 2011.

Construction work started in September, funded by the Manx Lottery Trust and Tower Insurance, and required the railway to transport 140 tons of rock to the site, for the platform extension foundations and infill.

The building was constructed by volunteer joiner Stephen Goody to match the style of the canopy, shop and booking office, and the entire area was completed in time for the Christmas services.

Download coordinates as: Despite being under one mile long, the railway does have intermediate stations, although only one of them is still operational for passengers and the other forms the site of the current passing loop when two trains are in operation (this was extended in 2011 to allow trains with more coaches to pass each other unhindered); the outer terminus is home to the visitor centre whilst the inner station houses all the running sheds and the railway's workshops.

Until the arrival of Annie, one of the railway's two diesel locomotives was renamed as "Blitzen" for the day, originally the traditional name of "Rudolph" was applied but this was changed in 1997 following requests.

As part of the railway's fundraising drive for a new station building at Sea Lion Rocks terminus some special event days were run at weekends in either July or August, during the school summer holidays, for three years from 2000 to 2002.

The Teddy Bear's Picnic wasn't repeated due to competition from the Government railways own event not making it financially viable.

A day of free open-air concerts from Manx groups and musicians were performed at Sea Lion Rocks, this event was deemed a great success and has been repeated every year since.

As part of 1998's Steam 125 celebration, the railway played host to a hand-made rail bike built by Dr Karl Pischl in Austria.