US citizens can travel to Iceland on holiday or business for 90 days or less, in accordance with the Visa Waiver Program.
US citizens wanting to stay longer or reside in Iceland must apply for a residence permit at the Icelandic Directorate of Immigration.
Travelers to Iceland must be in possession of a passport, valid at least for 90 days beyond their intended stay. In addition to that, nationals of many countries are required to obtain a visa prior to entering Iceland. A list of those countries can be seen by clicking here.