You hold valid UK visa Can you travel from Northern Ireland to Republic of for 3 days by land without getting a republic Ireland?

No, you cannot travel from Northern Ireland to the Republic of Ireland for 3 days by land without getting a republic Ireland visa. Although Northern Ireland is part of the United Kingdom, the Republic of Ireland is a separate country and requires a valid visa for entry. As a UK visa holder, you may only travel to the Republic of Ireland for a short stay (up to 90 days) without a visa if you are using a valid passport from the UK, the European Economic Area (EEA), or Switzerland.