The 1883 eruption of Krakatoa (Indonesian: Letusan Krakatau 1883) in the Sunda Strait began on 20 May 1883 and peaked on the late morning of Monday, 27 August 1883, when over 70% of the island of Krakatoa and its surrounding archipelago were destroyed as it collapsed into a caldera.

The eruption was one of the deadliest and most destructive volcanic events in recorded history. The explosion was heard 3,110 kilometres (1,930 mi) away in Perth, Western Australia, and Rodrigues near Mauritius, 4,800 kilometres (3,000 mi) away. The sound was reportedly heard in 50 different locations around the world and the sound wave is recorded to have travelled the globe seven times. At least 36,417 deaths are attributed to the eruption and the tsunamis it created.

Significant additional effects were also felt around the world in the days and weeks after the volcano's eruption. Additional seismic activity was reported until February 1884, but any reports after October 1883 were later dismissed by Rogier Verbeek's investigation into the eruption.

Krakatoa (), also transcribed Krakatau (; Indonesian: Krakatau), is a caldera in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The caldera is part of a volcanic island group (Krakatoa Archipelago) comprising four islands. Two, Lang and Verlaten, are remnants of a previous volcanic edifice destroyed in eruptions long before the famous 1883 eruption; another, Rakata, is the remnant of a much larger island destroyed in the 1883 eruption.

In 1927, a fourth island, Anak Krakatau, or "Child of Krakatoa", emerged from the caldera formed in 1883. There has been new eruptive activity since the late 20th century, with a large collapse causing a deadly tsunami in December 2018.