In the northeast, the narrow Strait of Malacca separates the island from the Malay Peninsula, which is an extension of the Eurasian continent.

The Bukit Barisan mountains, which contain several active volcanoes, form the backbone of the island, while the northeastern area contains large plains and lowlands with swamps, mangrove forest and complex river systems.

Sumatra has a wide range of plant and animal species but has lost almost 50% of its tropical rainforest in the last 35 years.

[2] The widespread deforestation and other environmental destruction in Sumatra and other parts of Indonesia has often been described by academics as an ecocide.

[13] In the late 13th century, Marco Polo referred to the kingdom as Samara, while his contemporary fellow Italian traveller Odoric of Pordenone used the form Sumoltra.

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.

[18]: 79–80  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[19] By the end of the 12th century, Srivijaya had been reduced to a kingdom, and its dominant role in South Sumatra ended with the last king, Ratu Sekekhummong, who founded the milestone of Kepaksian Sekala Brak in the 13th century AD with the Dalom building.

[19][20] 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 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.

[32] The largest indigenous ethnic groups in Sumatra are Malays, Minangkabaus, Bataks, Acehnese, and Lampungs.

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)[33] 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)).

Like all parts of Indonesia, Indonesian (which was based on Riau Malay) is the official language and the main lingua franca.

[38] The longest axis of the island runs approximately 1,790 km (1,110 mi) northwest–southeast, crossing the equator near the centre.

The interior of the island is dominated by two geographical regions: the Barisan Mountains in the west and swampy plains in the east.

On 26 December 2004, the western coast and islands of Sumatra, particularly Aceh province, were struck by a tsunami following the Indian Ocean earthquake.

Lake Toba is the site of a supervolcanic eruption that occurred around 74,000 years ago, representing a climate-changing event.

To the east, big rivers carry silt from the mountains, forming the vast lowland interspersed by swamps.

Arabica coffee from the regions of Gayo, Lintong and Sidikilang is typically processed using the Giling Basah (wet hulling) technique, which gives it a heavy body and low acidity.

Sumatra supports a wide range of vegetation types that are home to a rich variety of species, including 17 endemic genera of plants.

[45] Unique species include the Sumatran pine which dominates the Sumatran tropical pine forests of the higher mountainsides in the north of the island and rainforest plants such as Rafflesia arnoldii (the world's largest individual flower), and the titan arum (the world's largest unbranched inflorescence).

[3][4][5][6] Several unconnected railway networks built during Netherlands East Indies exist in Sumatra, such as the ones connecting Banda Aceh-Lhokseumawe-Besitang-Medan-Tebingtinggi-Pematang Siantar-Rantau Prapat in Northern Sumatra (the Banda Aceh-Besitang section was closed in 1971, but is currently being rebuilt).