The Tenroku gas explosion (天六ガス爆発事故, Tenroku gasu bakuhatsu jiko) occurred at approximately 5:47 pm on 8 April 1970 in Osaka, Japan, when a gas leak during construction at Tenjimbashisuji Rokuchōme Station in downtown Osaka resulted in a massive explosion and fire that killed 79 people, injured 420 others, and damaged 495 buildings.

[2] At the time, Japan had been experiencing widespread modernization, and large-scale developments of cities like Tokyo, Osaka, and Sapporo were not uncommon.

[3] The constant construction work and vibrations from surface traffic also affected the buried utility lines, to the point of damaging them.

The explosion was so large and powerful that it completely destroyed around 30 buildings and tossed the concrete slabs covering the tunnel into the air and onto victims.

[2][3][4][5] The emergency response to the explosion was stymied by mass confusion: the Osaka Municipal Fire Department's central dispatch room was being moved to a new building that day, and many victims with less-serious wounds reached hospitals themselves with little information as to what happened or what the full extent of their injuries were.

[5] The gas flow to the area was shut off within four hours, and by 9:40 pm firefighters reported the fires caused by the explosion were under control.

Reportedly, none of the victims were foreign visitors from Expo '70,[3] which was not affected by the explosion, though the Japan Gas Association's pavilion there was closed for 12 hours afterward.