On most international maps, the name is Borneo. In Indonesia, the same island is called Kalimantan. The difference can look like a matter of language, but the two names carry very different histories.
The story begins in 1521, when the remaining ships of Ferdinand Magellan’s expedition reached the northern coast of a vast island in Southeast Asia. Antonio Pigafetta, the expedition’s chronicler, recorded the name of a port they encountered: Brunei.
European maps gradually turned that name into Borne, then Bore, and eventually Borneo, the name that would become established in European literature and, later, international usage.
Indonesia eventually chose another name. Today, Kalimantan refers to the Indonesian portion of the island, covering about 544,150 square kilometres, or roughly 73 percent of Borneo. Sabah and Sarawak make up most of the Malaysian portion, while Brunei occupies a much smaller area on the northern coast.
But why Kalimantan?
A Name With No Single Origin
There is no universally accepted explanation for where the word Kalimantan came from. Several theories have circulated for centuries, reflecting the island’s long history of contact among different languages and communities.
One interpretation connects it to Sanskrit, from kalamantana, combining kala, associated with time, season, or weather, and manthana, meaning to churn or stir. Another theory, associated with the 19th-century colonial historian John Crawfurd, links Kalimantan to klemantan, a name for a type of mango found in the region.
Other explanations look to languages spoken in the archipelago. One connects kali, meaning river in Javanese, with mantan or pamantan, associated with something large in Ngaju Dayak, producing an interpretation along the lines of “great river.” There are also explanations rooted in Dayak oral traditions and others that trace the word to South Asian languages.
None has become definitive. The uncertainty matters because Kalimantan was never simply a new Indonesian translation of Borneo. The name had its own history in the region before it became the official name of an Indonesian province.
When Kalimantan Became a Political Name
The shift became more visible in the early 20th century, when the name began appearing in indigenous newspapers and political organizations.
In 1926, Housman Baboe, a Dayak official and journalist in Kuala Kapuas, established Borpena, short for Borneosche Pers en Nieuws-Agentschap. Two years later, he renamed the agency Kalpena, or Kalimantansche Pers en Nieuws-Agentschap. The change placed “Kalimantan” at the center of an emerging indigenous press identity.
A similar shift appeared in Banjarmasin. On March 23, 1930, A.A. Hamidhan founded Soeara Kalimantan, an indigenous daily newspaper that challenged the dominance of Dutch-language and colonial-oriented publications in the city.
The choice of name was significant. At a time when much of the island was still governed under Dutch colonial rule, using “Kalimantan” helped create a vocabulary of identity that was distinct from the colonial usage of Borneo. Hamidhan's newspaper repeatedly criticized the colonial government, and he was imprisoned several times because of his political activities.
The name also spread beyond the press. Youth organizations adopted “Kalimantan” in their names, and during the struggle for Indonesian independence it appeared in the names of armed and political groups fighting for the republic.
The word was gradually becoming more than a geographic label. It was becoming part of the political vocabulary of Indonesian nationalism.
The Decision Came After Independence
That transformation became official soon after Indonesia declared independence.
On August 19, 1945, two days after the proclamation, the Preparatory Committee for Indonesian Independence (PPKI) divided the new republic into eight provinces. One of them was Kalimantan, with Pangeran Mohammad Noor appointed as its first governor.
From that point, Kalimantan was no longer simply an alternative name used by newspapers or nationalist groups. It was the name of an administrative territory within the Indonesian state.
The province was later divided into smaller provinces. South Kalimantan, East Kalimantan, and West Kalimantan were established in 1956, Central Kalimantan followed in 1957, and North Kalimantan became Indonesia’s newest Kalimantan province in 2012 after being separated from East Kalimantan.
Today, those five provinces occupy most of Borneo’s southern and central territory. Across the border, Malaysia continues to use Borneo alongside the names Sabah and Sarawak, while Brunei retains its own historical identity on the northern coast.
So when Indonesians say Kalimantan, they are referring to the Indonesian part of an island the rest of the world generally calls Borneo. The difference emerged from a much longer process than a simple change of vocabulary: an old geographic name, an indigenous press, an anticolonial political identity, and finally the administrative language of an independent republic.
