The first direct detection of gravitational waves and the first observation of a binary black hole merger were made by the LIGO detectors on September 14, 2015. The signal, named GW150914, was observed by both LIGO detectors and had a peak gravitational-wave strain of 1.0 × 10⁻²¹. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal had a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 ± 180 Mpc, corresponding to a redshift of z = 0.09 ± 0.04. The initial black hole masses are 36 ± 5 M☉ and 29 ± 4 M☉, and the final black hole mass is 62 ± 4 M☉, with 3.0 ± 0.5 M☉c² radiated in gravitational waves. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger. The results confirm predictions of general relativity for the nonlinear dynamics of highly disturbed black holes. The observations provide unique access to the properties of space-time in the strong-field, high-velocity regime. The detectors, LIGO and Virgo, are designed to distinguish gravitational waves from local instrumental and environmental noise, to provide source sky localization, and to measure wave polarizations. The detectors are highly sensitive to gravitational waves, with a strain sensitivity of 3 to 5 times higher than initial LIGO in the most sensitive band. The results have significant implications for astrophysics, including the confirmation of binary black hole mergers and the constraints on the rate of stellar-mass binary black hole mergers in the local universe. The results also provide constraints on the properties of gravitational waves, including the Compton wavelength of the graviton. The observations are consistent with the predictions of general relativity in the strong-field regime of gravity.The first direct detection of gravitational waves and the first observation of a binary black hole merger were made by the LIGO detectors on September 14, 2015. The signal, named GW150914, was observed by both LIGO detectors and had a peak gravitational-wave strain of 1.0 × 10⁻²¹. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal had a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 ± 180 Mpc, corresponding to a redshift of z = 0.09 ± 0.04. The initial black hole masses are 36 ± 5 M☉ and 29 ± 4 M☉, and the final black hole mass is 62 ± 4 M☉, with 3.0 ± 0.5 M☉c² radiated in gravitational waves. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger. The results confirm predictions of general relativity for the nonlinear dynamics of highly disturbed black holes. The observations provide unique access to the properties of space-time in the strong-field, high-velocity regime. The detectors, LIGO and Virgo, are designed to distinguish gravitational waves from local instrumental and environmental noise, to provide source sky localization, and to measure wave polarizations. The detectors are highly sensitive to gravitational waves, with a strain sensitivity of 3 to 5 times higher than initial LIGO in the most sensitive band. The results have significant implications for astrophysics, including the confirmation of binary black hole mergers and the constraints on the rate of stellar-mass binary black hole mergers in the local universe. The results also provide constraints on the properties of gravitational waves, including the Compton wavelength of the graviton. The observations are consistent with the predictions of general relativity in the strong-field regime of gravity.