The 2004 Indian Ocean earthquake and tsunami (also known as the Boxing Day Tsunami occurred at 07:58:53 local time on 26 December, with an epicentre off the west coast of northern Sumatra, Indonesia. It was an undersea megathrust earthquake that registered a magnitude of 9.1–9.3 Mw.

A series of massive tsunami waves grew up to 30 m high once heading inland, after being created by the underwater seismic activity offshore. Communities along the surrounding coasts of the Indian Ocean were devastated, and the tsunamis killed an estimated 227,898 people in 14 countries, making it one of the deadliest natural disasters in recorded history. The direct results caused major disruptions to living conditions and commerce in coastal provinces of surrounded countries, including Aceh (Indonesia), Sri Lanka, Tamil Nadu (India) and Khao Lak (Thailand). Banda Aceh reported the largest number of deaths.

The earthquake was the third-largest ever recorded, the largest in the 21st century. The plight of the affected people and countries prompted a worldwide humanitarian response, with donations totalling more than US$14 billion.

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