Iceland was Christianized in the year 1000 CE, when Christianity became the religion by law. In Icelandic, this event is known as the kristnitaka (literally, "the taking of Christianity").

The vast majority of the initial settlers of Iceland during the settlement of Iceland in the 9th and 10th centuries CE were pagan, worshipping the Æsir (the Norse gods). Beginning in 980, Iceland was visited by several Christian missionaries who had little success; but when Olaf Tryggvason (who had converted around 998) ascended to the Norwegian throne, there were many more converts, and the two rival religions soon divided the country and threatened civil war.

After war broke out in Denmark and Norway, the matter was submitted to arbitration at the Althing. Law speaker and pagan Thorgeir Thorkelsson proposed "one law and one religion" after which baptism and conversion to Christianity became compulsory. Ari Thorgilsson's Book of the Icelanders, the oldest indigenous account of Iceland's Christianization describes how Icelanders agreed to convert to Christianity through a bargain whereby some pragmatic concessions were granted to the pagans in exchange for converting.