EU / EEA Citizens
As a member of the European Union (EU) all full citizens of other EU member states enjoy an automatic right to work and live in the Republic of Ireland and do not generally require a visa to reside in Ireland or an employment permit (although you will be required to register to secure an Irish ‘Public Service Number’ on arrival). A similar status also applies to full citizens of the European Economic Area (EEA) and Switzerland.
If you are not an EU citizen but entitled to citizenship of an EU country (perhaps through a parent or grandparent), it may be worth considering applying for dual citizenship, if this is option is available to you.
Non EU / EEA Citizens
For Non EU/EEA citizens, the approval and registration of immigration visas and employment permits are collectively managed by Ireland’s Department of Jobs, Enterprise & Innovation (DJEI), the Irish Naturalisation & Immigration Service (INIS) and the Irish Garda (Police) Immigration Bureau (GNIB).
It is essential for Non EU / EEA Assignees to secure the appropriate Irish visa and employment permit before your first arrival in Ireland and maintain its validity throughout the duration of your assignment.
Many Non EU / EEA countries are exempt from the requirement to hold an entry visa (See: https://www.dfa.ie/travel/visas/visas-for-ireland) but, even if you are exempt from having to apply for a visa, you will still need to satisfy immigration requirements on your arrival in Ireland and, if you are intending to stay in Ireland for more than 90 days, you will also need to separately register your residency in person shortly after arrival.