The current course of the Yellow River, China, involves an unusual 1500-km-long angular bend around the Ordos tectonic block, although sedimentary evidence suggests that the river once followed a more direct path eastward into the Bohai Sea. Geologic evidence reveals that the Yellow River formed in the Eocene as an eastward-draining river and developed its square bend around the Ordos block in late Miocene–early Pliocene time as a result of folding and uplift that are most probably related to the collision and penetration of India into Eurasia, as well as rifting around the Ordos block. The change in course of the Yellow River predates flat-lying Pliocene-Pleistocene sediment deposits that unconformably overlie folded Eocene-Miocene strata. The Yellow River provides a typical example of tectonic controls on the size, morphology, and longevity of rivers.