EU countries, Commonwealth countries and the USA do NOT need a visa.
Citizens of the European Union (EU) countries, as well as of Switzerland, Iceland, Liechtenstein and Norway may enter in Iceland with their national identity card, provided there is a photograph.

Schengen Visa holders are allowed to enter in Iceland
The Schengen Visa has made traveling between 25 member countries (22 European Union states and 3 non-EU members) much easier and less bureaucratic. Traveling on a Schengen Visa means that the visa holder can travel to any (or all) member countries using one single visa, thus avoiding the hassle and expense of obtaining individual visas for each country. A Schengen visa allows the holder to travel freely within the Schengen countries for a maximum stay of up to 90 days in a 6 months period.

See more information here: https://island.is/en/do-you-need-a-visa

How to get visa invitation letter

Confirmation letters for all authors of accepted papers who register for the conference will be issued by the PaperCept Conference Management System. This letter can be used to obtain a travel visa if required.

All authors of accepted papers will have the option to request an invitation letter through the registration system. This letter can be used to obtain a travel visa if required. Please note that only conference registrants will be issued the standard confirmation letter. We regret that we are unable to provide customized letters.

Letters confirming registration without an accepted paper may be issued by the conference organizers on an individual basis, after a participant has registered for the conference. Please contact us if you require a confirmation letter.