In this paper, we present a real-time multi-IMU visual-inertial navigation system (mi-VINS) that utilizes the information from multiple inertial measurement units (IMUs) and thus is resilient to IMU sensor failures. In particular, in the proposed mi-VINS formulation, one of the IMUs serves as the “base” of the system, while the rest act as auxiliary sensors aiding in state estimation. A key advantage of this architecture is the ability to seamlessly “promote” an auxiliary IMU as a new base, for example, upon detection of the base IMU failure, thus being resilient to the single point of sensor failure as seen in conventional VINS. Moreover, in order to properly fuse the information of multiple IMUs, both the spatial (relative pose) and temporal (time offset) calibration parameters between each sensor and the base IMU are estimated online. The proposed miVINS with online spatial and temporal calibration is validated in both simulations and real-world experiments, and is shown to be able to provide accurate localization and calibration even in scenarios with IMU sensor failures.