Barren Island is an island located in the Andaman Sea. It is the only confirmed active volcano in the Indian subcontinent, and the only active volcano along a chain of volcanoes from Sumatra to Myanmar. It is a part of the Indian Union territory of Andaman and Nicobar Islands, and lies about 138 km (86 mi) northeast of the territory's capital, Port Blair.

The first recorded eruption of the volcano dates back to 1787. Since then, the volcano has erupted more than ten times, with the most recent one being in 2022. After the first recorded eruption in 1787, further eruptions were recorded in 1789, 1795, 1803–04, and 1852. After nearly one and a half centuries of dormancy, the island had another eruption in 1991 that lasted six months and caused considerable damage.

The 1991 eruption was particularly harmful to the island's fauna. A team from the Geological Survey of India visited Barren Island on 8–9 April 1993 to assess the impact of the eruption on the distribution, habit, and abundance of animal species. The report found that the eruption had reduced the number of bird species and their population. The team only observed 6 of the 16 known species of birds on the island. The pied imperial pigeon (Ducula bicolor) was the most abundant among the 6 species observed. In a survey conducted at night, the team spotted one rat species (Rattus rattus) and 51 species of insects from eight orders. The report also noted that the volcano was still emitting gas at the time. There were eruptions in 1994–95 and 2005–07, the latter considered to be linked to the 2004 Indian Ocean earthquake. A lighthouse that was established in 1993 was destroyed by the recent eruptions.

A team from the National Institute of Oceanography spotted the volcano erupting on 23 January 2017. Abhay Mudholkar, the head of the team, said, "The volcano is erupting in small episodes of about five to ten minutes. During the day, only ash clouds were observed. However, after sundown, red lava fountains were spewing from the crater into the atmosphere and hot lava flowed streaming down its slopes."

Based on argon-argon dating of samples from Barren Island, it is now established that the oldest subaerial lava flows of the volcano are 1.6 million years old and the volcano is located on an oceanic crust which is roughly 106 million years old. All recorded eruptions lie on the low end of the Volcanic Explosivity Index. The 2017 eruption was recorded as a 2 on the index.

This volcanic island stands in the midst of a volcanic belt on the edge of the Indian and Burmese tectonic plates. Narcondam Island is a dormant volcano in the area, apart from volcanic seamounts like Alcock and Sewell. All the historical and recent eruptions (1789 and after) are confined within and around an active polygenetic cinder cone in a 2 km (1.2 mi) wide caldera that was formed by the Pleistocene collapse of a primitive cone of a stratovolcano. The remnant of the primitive volcanic cone forms a precipitous cliff around the island (commonly referred to as a caldera wall), with a break towards the west. The highest elevation on the island is 353 m (1,158 ft), with most of the primitive volcano underwater (standing on the seafloor 2,250 metres (7,380 ft) below sea level). The island is 3 km (1.9 mi) in diameter, with a total surface area of 8.34 km (3.22 sq mi). The rock types are basalt and andesite, with activity reported in late 2022.

The island is a protected area under Barren Island Wild Life Sanctuary.

True to its name, it has large areas of barren landscape. It is uninhabited by humans, though it has a small population of goats. Additionally, birds like pigeons, bats like flying foxes and a few rodent species such as rats are known to survive the harsh conditions.

A small population of feral goats was also found on the island, which surprised geologists. Later, it was found that they were surviving on two fresh water springs and thick vegetation. These goats were kept there by British sailors from a steamer leaving Port Blair in 1891.

The waters surrounding Barren Island are reputed to be among the world's top scuba diving destinations. Major attractions here are the crystal clear visibility, manta rays, interesting basalt formations, topography of past lava flows and fast growing coral gardens. This dive destination is remote but can be accessed by either a live-aboard ship or with scuba-operators based at Swaraj Island.

Barren Island belongs to the North and Middle Andaman administrative district, part of the Indian union territory of Andaman and Nicobar Islands.

The island is uninhabited.

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  Barren Island in 2020
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  Barren Island erupts
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  Crater on Barren Island in 2016
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  Outline map of the Andaman Islands, with the location of Barren Island highlighted (red circle)
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  Topography of the island
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  INS Saryu (P54), IN LCU 55 and IN LCU 58 approaching Barren Island
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  Barren Island seen from INS Saryu (P54) in 2021

• List of volcanoes in India

• Geological Survey of India: THE BARREN ISLAND VOLCANO
• Department of Earth Sciences, IIT Bombay
• Bhaumik, Subir (11 July 2005). "Andamans volcano is post-tsunami hit". BBC News. Retrieved 1 June 2013.
• Geological Survey of India