River Thames in London, England. People have lived along the banks of this river for thousands of years.

A river is a stream of water that flows through a channel on the surface of the ground. The passage where the river flows is called the river bed and the earth on each side is called a river bank. A river begins on high ground or in hills or mountains and flows down from the high ground to the lower ground, because of gravity. A river begins as a small stream, and gets bigger the farther it flows.