When was the first gravitational-wave event detected?

LIGO announced the first direct detection of gravitational waves on 11 February 2016, based on a signal observed on 14 September 2015. The waves came from the merger of two black holes more than a billion light-years away. This discovery confirmed a major prediction of Einstein’s general relativity and opened a new way of observing the universe. It marked the beginning of gravitational-wave astronomy.