GW170814 was a gravitational wave signal from two merging black holes, detected by the LIGO and Virgo observatories on 14 August 2017.

[1] On 27 September 2017, the LIGO and Virgo collaborations announced the observation of the signal, the fourth confirmed event after GW150914, GW151226 and GW170104.

It was the first binary black hole merger detected by LIGO and Virgo together.

[3] Analysis indicated the signal resulted from the inspiral and merger of a pair of black holes (BBH) with 30.5+5.7−3.0 and 25.3+2.8−4.2 times the mass of the Sun, at a distance of 540+130−210 megaparsecs (1.8+0.4−0.7 billion light years) from Earth.

The peak luminosity of GW170814 was 3.7+0.5−0.5×1049 W. General relativity predicts that gravitational waves have a tensor-like (spin-2) polarization.