Niagara Falls is a set of massive waterfalls located on the Niagara River in eastern North America, on the border between the United States and Canada. Niagara Falls comprises three separate waterfalls: the Horseshoe Falls, the American Falls, and the smaller, adjacent Bridal Veil Falls. While not exceptionally high, Niagara Falls is very wide. With more than 6 million cubic feet of water falling over the crestline every minute it is the most powerful waterfall in North America and possibly the best-known in the world.

Niagara Falls is renowned for its beauty, and is both a valuable source of hydroelectric power and a challenging project for environmental preservation. A popular tourist site for over a century, the natural wonder is shared between the twin cities of Niagara Falls, Ontario and Niagara Falls, New York.

The historical roots of Niagara Falls lie in the Wisconsin glaciation, which ended some 10,000 years ago. The North American Great Lakes and the Niagara River are effects of this last continental ice sheet, an enormous glacier that crept across the area from eastern Canada. The glacier drove through the area like a giant bulldozer, grinding up rocks and soil, moving them around, and deepening some river channels to make lakes. It dammed others with debris, forcing these rivers to make new channels. It is thought that there is an old valley, buried by glacial drift, at the approximate location of the present Welland Canal.