An Icelandic phone book, or a hotel guest list, or a hospital patient index, is typically sorted alphabetically by first name rather than by surname — a detail that looks like an odd formatting choice until you understand that most Icelandic surnames don't function the way surnames do almost everywhere else.
Why: most Icelandic "surnames" are patronymics
The large majority of Icelanders do not have an inherited family surname passed down generation to generation the way most of the world understands the term. Instead, their surname is typically a patronymic — built directly from their father's first name, with -son ("son of") or -dóttir ("daughter of") added. A man named Jón whose father is named Einar would typically be Jón Einarsson; his sister might be Kristín Einarsdóttir. Their children, in turn, would take a patronymic from Jón or Kristín's own first name, not from "Einarsson" or "Einarsdóttir" — meaning siblings and parents within the same household frequently carry entirely different surnames, and a surname tells you whose child someone is, not what family line they belong to.
This has a practical consequence for a visitor trying to find someone: two siblings booking the same hotel room or restaurant table under their own names will not share a surname the way a couple or family from most other countries would, so don't expect a reservation search by "family name" to work the way it does elsewhere — the first name is the more reliable search term.
This is also why Icelandic naming has historically included a matronymic option — a surname built from the mother's first name instead of the father's — available to parents who choose it, though the patronymic form remains the more common default.
Because surnames under this system are not shared identifiers across a family or lineage the way "Smith" or "Johnson" function in English-speaking countries, they are much less useful for looking someone up or distinguishing between people in a directory. First names carry that identifying weight instead, which is the direct, practical reason phone books, class registers and similar lists in Iceland are conventionally sorted by first name.
Family surnames exist, but they're the exception
A small number of Icelandic families carry an inherited family surname rather than a patronymic, typically grandfathered in from historical exceptions predating stricter modern naming law, or in some cases originating from families with foreign ancestry. These function more like a conventional surname elsewhere — shared across generations rather than regenerated from each parent's first name — but they represent a minority of the population rather than an available option most Icelanders can freely adopt today.
The naming committee
Iceland maintains an official Icelandic Naming Committee (Mannanafnanefnd), administered through Iceland's government services portal, responsible for reviewing proposed new first names — particularly names not already on an approved register — against rules rooted in Icelandic grammar and spelling conventions, including whether a name can be properly declined (modified for grammatical case) within the Icelandic language, and whether its spelling uses letters compatible with the Icelandic alphabet. The committee's remit and the underlying law have been subject to public debate and legal challenge over the years, including cases where parents contested a name's rejection, and specific current rules and the committee's exact ongoing role are worth verifying through current Icelandic government sources rather than assuming historical rules remain unchanged, since this is an area of law that has evolved.
The broader cultural point for a visitor is less about the specific bureaucratic mechanism and more about what it reflects: a deliberate, long-standing effort to keep Icelandic naming consistent with the structure of the Icelandic language itself, in a country that has otherwise taken conscious steps — through its language academy and broader linguistic policy — to keep the language relatively unchanged compared to how much English and many other European languages have shifted over the same period.
What this means in practice for a visitor
You'll see this system reflected in how Icelanders introduce themselves (first name, generally without volunteering a surname unless asked), how businesses and public directories are organized, and how last names on a boarding pass, hotel reservation or restaurant booking might look unfamiliar if you're used to surnames signaling a family unit. None of this requires you to do anything differently as a visitor beyond understanding it — using someone's first name is the norm, not a breach of formality, and asking a friendly, genuine question about how someone's name works is generally well received rather than considered rude, given how routinely the topic comes up with visitors.
What this guide does not cover
This article explains the general structure of patronymic naming and the historical role of Iceland's naming committee; it does not cover current, specific naming law in detail, which has changed over time and is better checked through official Icelandic government sources if you need precise legal information.