The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) Physics Frontiers Center runs a long-term millisecond pulsar (MSP) timing program with the goal of detecting and characterizing nHz-frequency gravitational waves (GWs), the most likely sources of which are a GW background (GWB) from a population of coalescing supermassive binary black holes (SMBBHs), and individual, nearby SMBBHs. These detections will open a new window on the GW spectrum, complementing the higher-frequency LIGO detections. NANOGrav currently uses the Arecibo and Green Bank telescopes to time 76 MSPs with the sub-microsecond timing precision necessary to detect small, correlated variations in pulse arrival times caused by GWs. We have also begun timing several pulsars with the VLA, demonstrating the utility of phased arrays for precision pulsar timing, and have developed a plan to use the ngVLA for future NANOGrav timing observations. We expect to observe ~200 MSPs with the ngVLA; this significant increase in MSP number will result from a combination of more sensitive pulsar surveys (e.g. with FAST) and the increased sensitivity of the ngVLA, making it feasible to time some known, fainter pulsars with good precision. Indeed, a key benefit of the ngVLA is its increased sensitivity, relative to current instruments, at frequencies typically used for pulsar timing, as these higher frequencies mitigate the corrupting effects of the interstellar medium. Our requirements for the ngVLA include: a wide bandwidth (using observing ands of 1-4 or 2-8 GHz) for robust dispersion measure determination; sub-array capability; 10-20 observing hours per week; and good sky coverage to allow the best possible spatial distribution of, thus maximizing our GW sensitivity. We note that by the time the ngVLA is in use, the GWB and likely one or more individual GW-emitting SMBBHs will have been detected; additionally, several synergistic facilities for space-based GW detection and electromagnetic follow-up will be in operation. Thus, the ngVLA will be vital to NANOGrav’s transition from a focus on detection to that of extracting exotic physics and other interesting science from low-frequency GW sources, especially through multi-messenger observations of individual SMBBHs.