  A present challenge in testing general relativity (GR) with binary black hole
gravitational wave detections is the inability to perform model-dependent tests
due to the lack of merger waveforms in beyond-GR theories. In this study, we
produce the first numerical relativity binary black hole gravitational waveform
in Einstein dilaton Gauss-Bonnet (EDGB) gravity, a higher-curvature theory of
gravity with motivations in string theory. We evolve a binary black hole system
in order-reduced EDGB gravity, with parameters consistent with GW150914. We
focus on the merger portion of the waveform, due to the presence of secular
growth in the inspiral phase. We compute mismatches with the corresponding
general relativity merger waveform, finding that from a post-inspiral-only
analysis, we can constrain the EDGB lengthscale to be
$\sqrt{\alpha_\mathrm{GB}} \lesssim 11$ km.
