The Kayapo (Portuguese: Caiapó [kajaˈpɔ]) people are an indigenous people in Brazil, living over a vast area across the states of Pará and Mato Grosso, south of the Amazon River and along the Xingu River and its tributaries. This location has given rise to the tribe's nickname of "the Xingu". They are one of the various subgroups of the great Mebêngôkre nation (meaning "people from the water's source"). The name Kayapo is used by neighboring groups rather than referring by the Kayapo to themselves; they refer to outsiders as Poanjos.

A type of sweet potato/tuber forms an important part of the Kayapó diet, and is sometimes named "caiapo", after the tribe. It is cultivated under that name in Japan, and has been found to decrease insulin resistance in type 2 diabetic patients.

In the 18th century, in the northeastern region of the present state of São Paulo, the Kayapó tribe first encountered Portuguese-Brazilian bandeirantes, who were looking for gold, among other precious stones and metals, as well as indigenous slaves. As a result, the Kayapó left the area and migrated to the west.

In the 1950s and 1960s, the Brazilian government contacted the "warlike" Kayapós with the intention of making peace with them. As a result, most Kayapós are currently in-contact with and aware-of modern Brazilian society.

The Kayapo tribe lives alongside the Xingu River in the most east part of the Amazon Rainforest, in the Amazon basin, in several scattered villages ranging in population from one hundred to one thousand people in Brazil. Their land consists of tropical rainforest savannah (grassland) and is arguably the largest tropical protected area in the entire world, covering 11,346,326 hectares (28,037,380 acres) of Neotropical forests and scrubland containing many endangered species. They have small hills scattered around their land and the area is criss-crossed by river valleys. The larger rivers feed into numerous pools and creeks, most of which lack official names.

In 2018, there was an estimated 8,638 Kayapo people, which is an increase from 7,096 in 2003. Subgroups of the Kayapo include the Xikrin, Gorotire, Mekranoti, and Metyktire. Their villages typically consist of a dozen huts. A centrally located hut serves as a meeting place for village men to discuss community issues.

The term Kayapo, also spelled Caiapó or Kaiapó, came from neighboring peoples in the early 19th century and means "those who look like monkeys". This name is probably based on a Kayapó men's ritual involving monkey masks. The autonym for one village is Mebêngôkre, which means "the men from the water hole." Other names for them include Gorotire, Kararaô, Kuben-Kran-Krên, Kôkraimôrô, Mekrãgnoti, Metyktire, and Xikrin.

The Kayapó often don intricate, black body painting covering their entire bodies, with unique designs and patterns to each person. They believe that their ancestors learned the ways of life from insects, so they paint their bodies to mimic the invertebrates and to better communicate with the great spirit that exists in all things. The black body paint also allows them to blend into their surroundings when hunting in the forests. To help find their way through the jungle, the Kayapó paint their legs with a red pigment that rubs-off on the surrounding plants as they traverse through the vegetation. The colors that a Kayapó wears are representative of their tribe's colors.