Millimeter-wave (mmWave) band above 100 GHz has been widely analyzed in recent years, attributed to its potential for ultrafast wireless communications and high precision radar target detection. However, the mmWave systems are facing security threats induced by eavesdroppers or jammers, due to the mmWave beam scattering and diffraction properties. Efficient and flexible generation and synchronization of broadband mmWave chaos are essential for higher-security applications in the mmWave band. Herein, we propose and experimentally achieve a photonics-based mmWave chaos generation and synchronization scheme. The optoelectronic feedback loop-based D-band chaos source is successfully achieved with the carrier frequency of 120 GHz, seamlessly connecting the mmWave band and the optical-wave band. A mmWave chaos can be successfully synchronized by a neural network (NN) after a 0.2-m line-of-sight (LOS) wireless link with a correlation coefficient (C.C) up to 92.16%, greatly simplifying the system complexity of the hardware-based receiver. To the best of our knowledge, this is the first time that chaos in the mmWave region above 100 GHz is generated and then intelligently synchronized successfully. This approach of photonic mmWave chaos generation and synchronization will be a significant complement to the chaos application at the mmWave band, even facilitating the bridging of the terahertz (THz) gap in the future.