Iguazú Falls or Iguaçu Falls (Guarani: Chororõ Yguasu [ɕoɾo'ɾõ ɨɣʷa'su], Spanish: Cataratas del Iguazú [kataˈɾatas ðel iɣwaˈsu]; Portuguese: Cataratas do Iguaçu [kɐtɐˈɾatɐz du iɡwɐˈsu]) are waterfalls of the Iguazu River on the border of the Argentine province of Misiones and the Brazilian state of Paraná.

[3] Legend has it that a deity planned to marry a beautiful woman named Naipí, who fled with her mortal lover Tarobá in a canoe.

[3] The first European to record the existence of the falls was the Spanish Conquistador Álvar Núñez Cabeza de Vaca in 1541.

The columnar basalt rock sequences are part of the 1,000-metre-thick (3,300 ft) Serra Geral formation within the Paleozoic-Mesozoic Paraná Basin.

The tops of these sequences are characterized by 8–10 m (26–33 ft) of highly resistant vesicular basalt and the contact between these layers controls the shape of the falls.

[4][1] Numerous islands along the 2.7-kilometre-long (1.7 mi) edge divide the falls into many separate waterfalls and cataracts, varying between 60 and 82 m (197 and 269 ft) high.

Left of this canyon, another part of the river forms 160–200 individual falls, which merge into a single front during the flood stage.

The water of the lower Iguazu collects in a canyon that drains into the Paraná River, a short distance downstream from the Itaipu Dam.

[7][8] The first proposal for a Brazilian national park aimed at providing a pristine environment to "future generations", just as "it had been created by God" and endowed with "all possible preservation, from the beautiful to the sublime, from the picturesque to the awesome" and "an unmatched flora" located in the "magnificent Iguaçu waterfalls".

These were the words used by André Rebouças, an engineer, in his book Provinces of Paraná, Railways to Mato Grosso and Bolivia, which started up the campaign aimed at preserving the Iguaçu Falls in 1876.

Other walkways allow access to the elongated stretch of falls across the forest on the Argentine side and to the boats that connect to San Martin Island.

During the summer of 2006, a severe drought caused the Iguazu River to become diminished, reducing the amount of water flowing over the falls to 300 cubic metres per second (11,000 cu ft/s) until early December.