Jatun Mayu (Quechua hatun, jatun big, great, mayu river, "great river") is a Bolivian river in the Cochabamba Department, Tiraque Province, Tiraque Municipality and south of it in the Arani Province, Vacas Municipality. It is one of the most important tributaries of Parqu Qucha, a lake north west of Vacas. It originates north east of Punata. It changes its directions from north west to north, then near Palca it apruptly turns to the south east.