The Common Travel Area (CTA; Irish: Comhlimistéar Taistil) is an open borders area comprising the United Kingdom, the Republic of Ireland, the Isle of Man, and the Channel Islands. The British Overseas Territories are not included. Based on agreements that are not legally binding, the internal borders of the CTA are subject to minimal controls, if any, and can normally be crossed by British and Irish citizens with minimal identity documents with certain exceptions. The maintenance of the CTA involves co-operation on immigration matters between the British and Irish authorities.

In 2014, the British and Irish governments began a trial system of mutual recognition of each other's visas for onward travel within the CTA. As of June 2016, it applies to Chinese and Indian nationals and is limited to certain visa types. Other nationalities and those holding non-qualifying visas still require separate visas to visit both countries and may not avail of a transit visa exception if wishing to transit through the UK to the Republic of Ireland.

Since 1997, the Irish government has imposed systematic identity checks on air passengers coming from the UK and selective checks on sea passengers, and occasional checks on land crossings.