Following the IndiaAsia collision, continental blocks were extruded along large sinistral strikeslip faults. The longest such fault, the Ailao ShanRed River shear zone (ASRR), separated Indochina (Sundaland) from South China. The ~1000 kmlong, active Red River fault (RRF) extends along the north side of the Ailao Shan and currently exhibits a combination of rightlateral slip and normal faulting. Here, after discussing Tertiary and recent deformation along and around the RRF system (slipsense inversion, Oligocene/Quaternary offsets, Holocene slip rates, GPS measurements, earthquake mechanisms, etc.), we focus on its PlioQuaternary extent and kinematics from SE Yunnan of China into NW 〖JP2〗Vietnam, the western Gulf of Tonkin, and farther south all the way to Sabah. New data is used to corroborate that, past the triple junction with the Dien Bien Phu fault in NW Vietnam, most of the presentday rightlateral movement between South China and Sunda blocks continues chiefly southeastwards of the Day Nui Con Voi along the Da River fault, which is roughly parallel to the RRF and was the site of the 2020, MW 5. 0 Moc Chau earthquake. We further show that this active fault likely extends much farther south along the western edge of the OligoMiocene Yingehai/Song Hong basin and the SE coast of Vietnam (Quy Nhon shear zone), at least to the ‘Ile des Cendres’ volcanic alignment, and possibly farther to the western tip of the SabahBrunei thrust belt, offshore the active margin of northern Borneo. Finally, we discuss the kinematic consequences of largescale tectonic inversion across much of the South China Sea, between the Philippines, Taiwan Island, and Sunda.