The Great Southern & Western Railway was one of the main railway operations in Ireland between the late 19th century and early 20th century. The company was one of Ireland's "Big Four" railway operators, buying up smaller operations and expanding its route mileage for much of its lifetime.

The heart of the GS&WR was the Cork–Dublin mainline, the "Premier Line", a route still important to Ireland today. William Dargan was the driving force behind this and other GS&WR routes, although he was responsible for other routes in Ireland not part of the GS&WR. The company's base of operations was Kingsbridge Station in Dublin (now Heuston Station). At its height, the Great Southern & Western Railway included the West Cork Railway , the Limerick–Tralee line through North Kerry, the cross-country Limerick–Waterford line (formerly the Waterford & Limerick Railway ), the Dublin–Waterford line, as well as numerous branch lines.

The GS&WR was in serious competition with the Midland Great Western Railway for many years. Both ran services West out of Dublin, the GS&WR's services south to Limerick, Cork and Waterford, with the MGWR running to Galway, Westport, Ballina and Sligo (all these destinations are still served by rail today). The GS&WR also had designs on rail traffic to the West of Ireland. A branch was built from the Dublin–Cork mainline connecting to the MGWR Dublin–Galway line. This allowed the company to run services from Kingsbridge Station to Galway (across MGWR track from Athlone onwards). In the end, the GS&WR route was the one chosen by the single rail operator, Córas Iompair Éireann many years later, and is the route used today from Dublin to Galway.

Another area of competition was the GS&WR's purchase of railway operations along the West of Ireland from Limerick to Sligo. This line, recently dubbed the Western Railway Corridor, ran right through MGWR "territory". It did however, complement the radial MGWR lines from Dublin, allowing traffic from Limerick to Galway, Galway to Sligo, and connecting intermediate destinations in the West of Ireland.

The GS&WR is perhaps the most well-known of the former independant rail operators in Ireland's railway history, with GS&WR routes being some of the most used in Ireland, connecting Dublin to Limerick, Cork and Waterford. Indeed, the coats of arms of these cities decorate the facade of Heuston Station.

The GS&WR was amalgamated, along with the other main operators, to form the Great Southern Railways operator. The only company to escape amalgamation for some time was the cross-border Great Northern Railway .

See also

• History of rail transport in Ireland
• Rail transport in Ireland
• Iarnród Éireann