Ireland has ports in major ports in Dublin, Belfast, Cork, Rosslare, Derry and Waterford. Smaller ports exist in Arklow, Ballina, Drogheda, Dundalk, Dún Laoghaire, Foynes, Galway, Larne, Limerick, New Ross, Sligo, Warrenpoint and Wicklow. Ports in the Republic handle 3.6 million travellers crossing the sea between Ireland and Britain each year. The vast majority of heavy goods trade is done by sea. Ports in Northern Ireland handle 10 megatons (11 million short tons) of goods trade with Britain annually, while ports in the Republic of Ireland handle 7.6 Mt (8.4 million short tons).

Ferry connections between Ireland and Great Britain via the Irish Sea include routes from Dublin to Holyhead, Birkenhead, and Douglas, Isle of Man, Belfast to Stranraer, Birkenhead and Douglas, Isle of Man, Larne to Cairnryan and Troon, Cork to Swansea and Rosslare to Fishguard and Pembroke.

There are also ferry connections to France, from Rosslare to Roscoff and Cherbourg, and also from Cork to Roscoff.

Several (mainly hypothetical) plans to build an "Irish Sea tunnel" have been proposed. The first serious proposal was made in 1897, which was for a tunnel between Ireland and Scotland crossing the North Channel. Most recently, in 2004, the Institution of Engineers of Ireland proposed the "Tusker Tunnel" between the ports of Rosslare and Fishguard. In 1997 a British engineering firm, Symonds, proposed a rail tunnel from Dublin to Holyhead. Either of the two most recent proposals, at 80 km (50 mi), would be by far the longest tunnel in the world and would cost an estimated €20bn.

The railway network in Ireland was developed by various private companies during the 19th century, with some receiving government funding in the late 19th century. The network reached its greatest extent by 1920. A broad gauge of 1,600mm (5 ft 3in) was agreed as the standard the island, although there were also hundreds of kilometres of 914mm (3 ft) narrow gauge railways.

Long distance passenger trains in the Republic of Ireland are managed by Iarnród Éireann and connect most major towns and cities. In Northern Ireland, all rail services are provided by Northern Ireland Railways. Additionally, Ireland has one of the largest dedicated freight railways in Europe, operated by Bord na Móna totalling nearly 1,400 kilometres (870 mi).

In Dublin, two local rail networks provide transport in the city and its immediate vicinity. The Dublin Area Rapid Transit (DART) links the city centre with coastal suburbs. A new light rail system, the Luas, opened in 2004 and transports passengers to the central and western suburbs. Several more Luas lines are planned as well as an Dublin Metro. The DART is run by Iarnród Éireann and the Luas is run by Veolia under franchise from the Railway Procurement Agency. Under the Irish government's Transport 21 plan, the Cork to Midleton rail link was reopened in 2009. The re-opening of the Navan-Clonsilla rail link and the Western Rail Corridor are amongst future projects as part of the same plan.

Services in Northern Ireland are sparse in comparison to the rest of Ireland or Britain. A large railway network was severely curtailed in the 1950s and 1960s.

Current services includes suburban routes to Larne, Newry and Bangor, as well as services to Derry. There is also a branch from Coleraine to Portrush.

Motorists in Ireland drive on the left. There is an extensive road network and a developing motorway network fanning out from Dublin and Belfast in particular. Historically, land owners developed most roads and later Turnpike Trusts collected tolls so that as early as 1800 Ireland had a 16,100 kilometres (10,000 mi) road network.^[126] In recent years, the Irish Government launched a new transport plan that is the largest investment project ever in Ireland's transport system: investing €34 billion from 2006 until 2015. Work on a number of road projects has already commenced and a number of objectives have been completed.

Ireland's first mail coach services were contracted with the government by John Anderson with William Bourne in 1791 who also paid to improve the condition of the roads. The system of mail coaches, carriages and "bians" was further developed by Charles Bianconi, based in Clonmel, from 1815 as a fore-runner of the modern Irish public transportation system.

Today, the main bus companies are Bus Éireann in the Republic and Ulsterbus in Northern Ireland, both of which offer extensive passenger service in all parts of the island. Dublin Bus specifically serves the greater Dublin area and Metro operates services within the greater Belfast area.

Signposts and speed limits in the Republic of Ireland are shown in kilometres per hour, with speed limits having changed in 2005. Distance and speed limit signs in Northern Ireland use imperial units in common with the rest of United Kingdom.