The Tunguska Event, or Tunguska explosion, was a powerful explosion that occurred not far from the Podkamennaya (Lower Stony) Tunguska River in what is now Krasnoyarsk Krai in Russia, at 0 hours 13 minutes 35 seconds Greenwich Mean Time (around 07:14 local time) on June 30, 1908 (June 17 in the Julian calendar, in use locally at the time).
The explosion is believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3.1–6.2 mi) above the Earth's surface. Different studies have yielded varying estimates of the object's size, with general agreement that it was a few tens of metres across.
The number of scholarly publications on the problem of the Tunguska explosion between 1908 and 2009 may be estimated at about 1,000 (mainly in Russian). Many scientists have participated in Tunguska studies, the best-known of them being Leonid Kulik, Yevgeny Krinov, Kirill Florensky, Nikolay Vasiliev, and Wilhelm Fast.