This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Islam reaches the Indonesian archipelago with the founding of Samudera Pasai in 1267, on the north coast of Sumatra, the earliest well attested Islamic kingdom in Southeast Asia. From that founding point Islam spread further through the archipelago and into the Malacca Sultanate over the following two centuries, establishing itself across island Southeast Asia in a process that ran through the fifteenth century and beyond.
That spread ran mainly through trade networks and Sufi missionary orders rather than through conquest, a point worth stating plainly since conquest is the assumption many readers bring to any story of Islam's expansion. Merchants carried the faith along the same maritime trade routes that already linked the archipelago to India, Arabia and China, and Sufi teachers built on those trade contacts, embedding Islam in local courts and communities region by region rather than imposing it by force of arms.
What this changed for Islam's spread reaches into the present: Indonesia today has the largest Muslim population of any country in the world, a fact traceable back through the Malacca Sultanate to Samudera Pasai's founding in 1267 and to the trade and Sufi networks that carried the faith across the archipelago rather than any single conquering campaign.