On August 17, 2017 at 12:41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0 x 10(4) years. We infer the component masses of the binary to be between 0.86 and 2.26 M-circle dot, in agreement with masses of known neutron stars. Restricting the component spins to the range inferred in binary neutron stars, we find the component masses to be in the range 1.17-1.60 M-circle dot, with the total mass of the system 2.74(-0.01)(+0.04) M-circle dot. The source was localized within a sky region of 28 deg(2) (90% probability) and...