The Dublin and Kingstown Railway (D&KR), which opened in 1834, was Ireland’s first passenger railway. It linked Westland Row in Dublin with Kingstown Harbour (Dún Laoghaire) in County Dublin.

The D&KR was also notable for a number of other achievements besides being Ireland's first passenger railway: it operated an atmospheric railway for ten years; claimed the first use of a passenger tank engine; was the world's first commuter railway and was the first railway company to build its own locomotives.

On 30 June 1856 the Dublin and Wicklow Railway (D&WR) took over operation of the line from the D&KR with the D&KR continuing to lease out the line. The D&WR had formerly been known as the Waterford, Wicklow, Wexford and Dublin Railway (WWW&DR or 3WS). It changed its name to the Dublin Wicklow and Wexford Railway (DW&WR) in May 1860 and was ultimately renamed the Dublin and South Eastern Railway (D&SER) in 1907, a name which was retained until the amalgamation of the D&KR and D&SER with the Great Southern Railways on 1 January 1925. As of 1974, its independent existence of over 90 years by a railway company was only exceeded in the British Isles by the Great Western Railway and the Londonderry and Lough Swilly Railway.