Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the sixth-largest island in the world at 482,286.55 km<sup>2</sup> (182,812 mi.<sup>2</sup>), including adjacent islands such as Simeulue, Nias, the Mentawai Islands, Enggano, the various archipelagoes comprising the Riau Islands Province, Bangka and Belitung and the Krakatoa archipelago.
Sumatra is an elongated landmass spanning a diagonal northwest–southeast axis. The Indian Ocean borders the northwest, west, and southwest coasts of Sumatra, with the island chain of Simeulue, Nias, Mentawai, and Enggano off the western coast. In the northeast, the narrow Strait of Malacca separates the island from the Malay Peninsula, which is an extension of the Eurasian continent. In the southeast, the narrow Sunda Strait, containing the Krakatoa archipelago, separates Sumatra from Java. The northern tip of Sumatra is near the Andaman Islands, while off the southeastern coast lie the islands of Bangka and Belitung, Karimata Strait and the Java Sea. The Bukit Barisan mountains, which contain several active volcanoes, form the backbone of the island for effectively its entire length, while the northeastern area contains large plains and lowlands with swamps, mangrove forest and complex river systems. The equator crosses the island at its centre in West Sumatra and Riau provinces. The climate of the island is tropical, hot, and humid. Lush tropical rain forest once dominated the landscape.
Sumatra has a wide range of plant and animal species but has lost almost 50% of its tropical rainforest in the last 35 years. Many species are now critically endangered, such as the Sumatran ground cuckoo, the Sumatran tiger, the Sumatran elephant, the Sumatran rhinoceros, and the Sumatran orangutan. Deforestation on the island has also resulted in serious seasonal smoke haze over neighbouring countries, such as the 2013 Southeast Asian haze which caused considerable tensions between Indonesia and affected countries Malaysia and Singapore. The widespread deforestation and other environmental destruction in Sumatra and other parts of Indonesia has often been described by academics as an ecocide.
Etymology
thumb|Before it was known as Sumatra, the region was referred to as Melayu (also known as Malay in [[English language|English), named after the ancient Melayu Kingdom based in Jambi. The name Melayu appeared in early historical records, including inscriptions and Chinese chronicles, before being replaced by Sumatra in the 14th century.]]
Sumatra was known in ancient times by the Sanskrit names of ('Island of Gold') and Svarṇabhūmi ('Land of Gold'), because of the gold deposits in the island's highlands. The earliest known mention of the current form "Sumatra" was in 1017, when the local king Haji Sumatrabhumi ("king of the land of Sumatra") sent an envoy to China. Arab traders first referenced the island as Ramni in the ninth century, and later on as Lamuri, in reference to a kingdom near modern-day Banda Aceh which was the first landfall for traders. The island has also been known by other names, including Andalas or Percha Island. Scholars suggest that mention of Suwarnadwipa in the Hindu Epic the Ramayana may be a reference to Sumatra. According to experts on The Ramayana, the epic is one of the first sources to document the relationship between India and the Indonesian archipelago.
In the late 13th century, Marco Polo referred to the kingdom as , while his contemporary fellow Italian traveller Odoric of Pordenone used the form . Later in the 14th century the local form "Sumatra" became popular abroad due to the rising power of the kingdom of Samudera Pasai and the subsequent Sultanate of Aceh.
From then on, subsequent European writers mostly used Sumatra or similar forms of the name for the entire island.
History
By the year 692 CE, the Melayu Kingdom was absorbed by Srivijaya. Srivijaya's influence waned in the 11th century, specifically in the year 1025, after suffering defeat at the hands of the Chola Empire in southern India At the same time, the spread of Islam in Indonesia occurred gradually and indirectly, starting from the western regions such as the Sumatra area which became the first place for the spread of Islam in the archipelago, then Java, then to the eastern regions of Indonesia, Sulawesi and Maluku. The island of Sumatra is also an area in the archipelago that received the spread of Islam first compared to other islands or other areas. At the beginning and end of the 13th century the formation of the kingdom, the king of the Samudra kingdom had converted to Islam. Marco Polo visited the island in 1292, and his fellow Italian Odoric of Pordenone in 1321.
Aceh in the north of Sumatra became known in the 16th century as trading centre for the pepper trade by shipping quality piperaceae (pepper). Aceh became the main commercial centre of the Aceh Sultanate and trading routes were established to the Mediterranean via the Red Sea to rival the Portuguese shipping lanes. The reign of Iskandar Muda is known as the golden age of Sumatra because he extended the cultural influence of the Aceh Sultanate to Padang and Johor. The Aceh Sultanate sustained the rivalry with the Johor sultanate, the Dutch, and the Portuguese throughout the 16th and 17th century. When the Dutch were weakened in the 18th century the British empire began to actively intervene in Aceh, establishing close relations between Banda Aceh and Penang. In the 17th and 18th century the Aceh Sultanate battled the Siak sultanate in the south of Sumatra. The port city of Banda Aceh was recorded in European historical writings since the 13th century. In terms of economic development the port of Banda Aceh only started to face competition in the 18th century when more ports were constructed in Sumatra for maritime transport. Nevertheless, major pepper suppliers used the port of Banda Aceh at the beginning of the 19th century. The port in Medan grew swiftly in the late 19th and early 20th century. Meanwhile the medium sized port of Palembang faced a stiff economic decline as the heritage of the Srivijaya empire was superseded by the economic policy of the Singhasari and Majapahit. The Palembang sultanate experienced a terminal decline in the early 19th century.
With the coming of the Dutch Empire, the many Sumatran princely states gradually fell under their control. Aceh posed major obstacles, as the Dutch were involved in the long and costly Aceh War (1873–1903).
During the Second World War, Japan invaded Sumatra in 1942.
The Free Aceh Movement fought against Indonesian government forces in the Aceh Insurgency from 1976 to 2005. Security crackdowns in 2001 and 2002 resulted in several thousand civilian deaths.
The island was heavily impacted by both the 1883 Krakatoa eruption and the 2004 Indian Ocean earthquake and tsunami.
Demographics
Sumatra's population as of mid 2025 was estimated to be about 62,259,500 ; it has about the same number of inhabitants as South Africa, making it the fifth-most populous island in the world. Yet because it is such a large island, it is not densely populated: it has an average of about 129 people per km<sup>2</sup>.
Ethnic groups
right|thumb|250px|Map of the ethnic groups of Sumatra.
The largest indigenous ethnic groups in Sumatra are Malays, Minangkabaus, Bataks, Acehnese, and Lampungs. Other major non-indigenous ethnic groups are Javanese, Sundanese, and Chinese.
Below are 11 largest ethnic groups in Sumatra based on the 2010 census (including Riau Islands, Bangka Belitung, Nias, Mentawai, Simeulue and islands around it)
{| class="wikitable"
!Ethnic groups
!Population
|-
|Javanese
|15,239,275
|-
|Bataks
|7,302,330
|-
|Minangkabau
|5,799,001
|-
|Ethnic groups from South Sumatra
|4,826,272
|-
|Malays
|4,016,182
|-
|Ethnic groups from Aceh
|3,991,883
|-
|Ethnic groups from Jambi
|1,379,351
|-
|Sundanese
|1,231,888
|-
|Ethnic groups from Lampung
|1,109,601
|-
|Nias
|1,021,267
|-
|Other
|2,086,804
|}
Languages
thumb|Speakers of Acehnese.
thumb|upright|[[Kedukan Bukit Inscription, using Pallava alphabet, is the oldest surviving specimen of the Old Malay language in South Sumatra, Indonesia.]]
There are over 52 languages spoken, all of which (except Chinese and Tamil) belong to the Malayo-Polynesian branch of the Austronesian language family. Within Malayo-Polynesian, they are divided into several sub-branches: Chamic (which are represented by Acehnese in which its closest relatives are languages spoken by Ethnic Chams in Cambodia and Vietnam), Malayic (Malay, Minangkabau and other closely related languages), Northwest Sumatra–Barrier Islands (Batak languages, Gayo and others), Lampungic (includes Proper Lampung and Komering) and Bornean (represented by Rejang in which its closest linguistic relatives are Bukar Sadong and Land Dayak spoken in West Kalimantan and Sarawak (Malaysia)). Northwest Sumatra–Barrier Islands and Lampungic branches are endemic to the island. Like all parts of Indonesia, Indonesian (which was based on Riau Malay) is the official language and the main lingua franca. Although Sumatra has its own local lingua franca, variants of Malay like Medan Malay and Palembang Malay are popular in North and South Sumatra, especially in urban areas. Minangkabau (Padang dialect) is popular in West Sumatra, some parts of North Sumatra, Bengkulu, Jambi and Riau (especially in Pekanbaru and areas bordered with West Sumatra) while Acehnese is also used as an inter-ethnic means of communication in some parts of Aceh province.