The Niagara Falls straddle the international border between the Canadian province of Ontario and the U.S. state of New York. The falls are 17 miles (27 km) north-northwest of Buffalo, New York and 75 miles (121 km) south-southeast of Toronto, Ontario, between the twin cities of Niagara Falls, Ontario, and Niagara Falls, New York.

Niagara Falls is composed of two major sections separated by Goat Island: the Horseshoe Falls, which today is entirely on the Canadian side of the border, and the American Falls on the American side. The smaller Bridal Veil Falls are also located on the American side, separated from the main falls by Luna Island.

Niagara Falls were formed when glaciers receded at the end of the last ice age, and water from the newly formed Great Lakes carved a path through the Niagara Escarpment on its way to the Atlantic Ocean. While not exceptionally high, the Niagara Falls are very wide and are the most powerful waterfalls with the greatest volume of water in North America.

Niagara Falls are renowned both for their beauty and as a valuable source of hydroelectric power.

Niagara Falls is divided into the Horseshoe Falls and the American Falls. The Horseshoe Falls drop about 173 feet (53 m), and the height of the American Falls varies between 70?100 feet (21?30 m) because of the presence of giant boulders at its base. The larger Horseshoe Falls are about 2,600 feet (790 m) wide, while the American Falls are 1,060 feet (320 m) wide.

Viewpoints on the American shore generally are astride or behind the falls whereas the Canadian shore directly faces the falls.

Peak numbers of visitors occur in the summertime, when Niagara Falls are both a daytime and evening attraction. From the Canadian side, floodlights illuminate both sides of the falls for several hours after dark (until midnight). The number of visitors in 2008 is expected to total 20 million and by 2009, the annual rate is expected to top 28 million tourists a year. The oldest and best known tourist attraction at Niagara Falls is the Maid of the Mist boat cruise, named for an ancient Ongiara Indian mythical character, which has carried passengers into the rapids immediately below the falls since 1846. Cruise boats operate from boat docks on both sides of the falls.