On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a transient gravitational-wave signal from the merger of two black holes. The signal, named GW150914, was observed simultaneously by the LIGO Hanford and Livingston observatories at 09:50:45 UTC. The waveform matched the predictions of general relativity for the inspiral and merger of a pair of black holes, followed by the ringdown of the resulting single black hole. The signal had a peak gravitational-wave strain of \(1.0 \times 10^{-21}\) and a matched-filter signal-to-noise ratio of 24. The source was located at a luminosity distance of \(410^{+160}_{-180}\) Mpc, corresponding to a redshift of \(z = 0.09^{+0.03}_{-0.04}\). The initial black hole masses were \(36^{+1}_{-4}M_{\odot}\) and \(29^{+4}_{-4}M_{\odot}\), with the final black hole mass being \(62^{+4}_{-4}M_{\odot}\), radiating \(3.0^{+0.5}_{-0.5}M_{\odot}c^2\) in gravitational waves. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger, providing unique access to the properties of black holes and the strong-field regime of gravity.On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a transient gravitational-wave signal from the merger of two black holes. The signal, named GW150914, was observed simultaneously by the LIGO Hanford and Livingston observatories at 09:50:45 UTC. The waveform matched the predictions of general relativity for the inspiral and merger of a pair of black holes, followed by the ringdown of the resulting single black hole. The signal had a peak gravitational-wave strain of \(1.0 \times 10^{-21}\) and a matched-filter signal-to-noise ratio of 24. The source was located at a luminosity distance of \(410^{+160}_{-180}\) Mpc, corresponding to a redshift of \(z = 0.09^{+0.03}_{-0.04}\). The initial black hole masses were \(36^{+1}_{-4}M_{\odot}\) and \(29^{+4}_{-4}M_{\odot}\), with the final black hole mass being \(62^{+4}_{-4}M_{\odot}\), radiating \(3.0^{+0.5}_{-0.5}M_{\odot}c^2\) in gravitational waves. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger, providing unique access to the properties of black holes and the strong-field regime of gravity.