The Middle Fork Kings River is a major tributary of the Kings River in the U.S. state of California. The river flows 37.2 miles (59.9 km)[1] in a generally southwest direction, entirely within Kings Canyon National Park and the Sierra Nevada. Its drainage basin is roughly 500 square miles (1,300 km2) in size. The river joins the South Fork Kings River at its mouth to form the main stem of the Kings River.