Abstract: The LIGO detections of gravitational waves (GWs) from black hole mergers mark the beginning of the era of GW astronomy. The coming years hold great promise for GW detections of black hole binaries across the mass scale, including supermassive black hole (SMBH) inspiral and merger. Pulsar timing experiments, in particular, should soon detect GW signatures from SMBH binaries. I will review current theoretical predictions for these GW signatures, including recent results that utilize the Illustris cosmological hydrodynamic simulations to construct the most comprehensive SMBH binary inspiral models to date. These models predict that the stochastic GW background from SMBH binaries should be detected in less than 10-15 years for a wide range of assumptions. Finally, I will briefly describe our ongoing work to model and identify actively-accreting SMBHs in merging host galaxies, prior to the GW-dominated regime.