The Great Northern Railway (Ireland) (GNR(I) or GNRI) was an Irish railway company formed in 1876 by a merger of the Irish North Western Railway (INW), Northern Railway of Ireland, and Ulster Railway. The Ulster Railway was the GNRI's oldest constituent, having opened between Belfast and Lisburn in 1839 and extended in stages to reach Clones in 1863. The Northern Railway of Ireland was itself formed by a merger of the Dublin and Drogheda Railway (D&D) with the Dublin and the Belfast Junction Railway (D&BJct).

The Ulster, D&D and D&BJct railways together formed the main line between Dublin and Belfast, with the D&BJct completing the final section in 1852 to join the Ulster at Portadown. The GNRI's other main lines were between Derry and Dundalk and between Omagh and Portadown. The Omagh-Portadown link allowed GNRI trains between Derry and Belfast to compete with the Belfast and Northern Counties Railway, and both this and the Dundalk route gave connections between Derry and Dublin. These main lines supported the development of an extensive branch network serving the southwest half of Ulster and northern counties of Leinster. The GNRI became Ireland's most prosperous railway company and second largest railway network.

In its early years, the GNRI had closely imitated the image of its English namesake, adopting a pleasant apple green finish for its steam locomotives and a varnished teak finish for its passenger coaches. Later the company adopted its famous pale blue livery for locomotives, with the frames and running gear picked out in scarlet.

rowth and partition

In the early 20th century increasing traffic led the GNRI to consider introducing larger locomotives. The Great Southern and Western Railway had introduced express passenger locomotives with a 4-6-0 wheel arrangement, and the GNRI wanted to do the same. Unfortunately the lifting shop in the GNRI Dundalk works was too short to build or overhaul a 4-6-0, so the company persisted with 4-4-0 locomotives for even the heaviest and fastest passenger trains. This led to the GNRI to order a very modern and powerful class of 4-4-0's, the Class V three cylinder compound locomotives built by Beyer, Peacock in 1932. This class has been compared with another famous V class, that introduced by the Southern Railway in England in 1930.

The Partition of Ireland in 1921 created an international frontier through the GNRI's territory. The new border crossed all three of its main lines and some of its secondary lines. The imposition of frontier controls caused some service disruption, with main line trains having to stop at both Dundalk and Goraghwood stations. This was not eased until 1947 when customs and immigration facilities for Dublin-Belfast expresses were opened at Dublin Amiens Street station (renamed Dublin Connolly in 1966) and Belfast Great Victoria Street station.

Nationalisation and division:

A combination of the increasing road competition facing all railways and a change in patterns of economic activity caused by the partition of Ireland reduced the GNRI's prosperity. The company modernised and reduced its costs by introducing modern diesel multiple units on an increasing number of services in the 1940s and 1950s and by making Dublin-Belfast expresses non-stop from 1948. Nevertheless by the 1950's the GNRI had ceased to be profitable and in 1953 the company was jointly nationalised by the governments of the Republic of Ireland and Northern Ireland. The two governments ran the railway jointly under a Great Northern Railway Board until 1958.

In May 1958, the Northern Ireland Government's desire to close many lines led to the GNRI Board being dissolved and the assets divided between the two states. All lines in Northern Ireland were transferred to the Ulster Transport Authority (UTA) and all lines in the Republic of Ireland were transferred to Córas Iompair Éireann (CIE). In an attempt at fairness, all classes of locomotive and rolling stock were also divided equally between the transport operators of the two states. Most classes of GNRI locomotive had been built in small classes, so this division left both railways with an operational and maintenance nightmare of many different designs all in small numbers.

The Northern Ireland government rapidly closed all GNRI lines in Northern Ireland except the Belfast-Dundalk and Portadown-Derry main lines and the Newry-Warrenpoint and Lisburn-Antrim branches. It made the Lisburn-Antrim branch freight-only from 1960 and closed the Portadown-Derry and Newry-Warrenpoint lines to all traffic in 1965. The Republic of Ireland government tried briefly to maintain services on lines closed at the border by the Northern Ireland government, but this was impractical, and the Republic had to follow suit in closing most GNRI lines south of the border. Since 1960 the Drogheda-Navan branch has survived for freight traffic only.

The Hill of Howth Tramway, in the northern suburbs of Dublin, was also acquired by CIE in the 1958 dissolution of the GNRI Board. It was closed down about a year later.

The Fintona horse tram:

The small County Tyrone town of Fintona was bypassed by the main line of the GNRI. Fintona was instead served by a one mile long branch line from "Fintona Junction" station. The service was operated by a horse drawn double-deck tram until closure of the line in 1957.

Preserved vehicles:

Four GNRI steam locomotives are preserved. The Railway Preservation Society of Ireland at Whitehead owns three of its 4-4-0's (one each of classes S, Q and V) and periodically operates one or more of them on special excursion trains on Northern Ireland Railways and Iarnród Éireann (successor to CIE) routes. A 2-4-2T locomotive is preserved at the Ulster Folk and Transport Museum at Cultra.

Some of its coaching stock has also been preserved. 1938 built dining car No.88 still sees use as part of the Railway Preservation Society of Ireland's Dublin based "heritage set" of coaches. Also operating in this set is a 1954 built brake coach No.9, although it currently carries the number 1949. The Downpatrick & County Down Railway also has an example of a third-class GNR six-wheeled carriage, in a unrestored condition.