The Chamorro people (/tʃɑːˈmɔːroʊ, tʃə-/; also Chamoru) are the Indigenous people of the Mariana Islands, politically divided between the United States territory of Guam and the encompassing Commonwealth of the Northern Mariana Islands in Micronesia, a commonwealth of the US. Today, significant Chamorro populations also exist in several US states, including Hawaii, California, Washington, Texas, Tennessee, Oregon, and Nevada, all of which together are designated as Pacific Islander Americans according to the US census. According to the 2000 census, about 64,590 people of Chamorro ancestry live in Guam and another 19,000 live in the Northern Marianas.

Precolonial society in the Marianas was based on a caste system, Chamori being the name of the ruling, highest caste.

After Spain annexed and colonized the Marianas, the caste system eventually became extinct under Spanish rule, and all of the Indigenous residents of the archipelago eventually came to be referred to by the Spanish exonym Chamorro. The name Chamoru is an endonym derived from the Indigenous orthography of the Spanish exonym. The digraph ch is treated as a single letter, hence both characters are capitalized at the beginning of a sentence or proper noun, much like ij in Dutch.

Some people theorize that Spanish definitions of the word Chamorro played a role in its being used to refer to the island's Indigenous inhabitants. Not only is "Chamorro" a Spanish surname; in Spanish it also means "leg of pork", "beardless [wheat]", "bald", "close-cropped", or "shorn/shaven/[hair or wool] cut close to the surface". Around 1670, a Catholic missionary reported that men were sporting a style in which their heads were shaven, save for a "finger-length" amount of hair at the crown. This hairstyle has often been portrayed in modern-day depictions of early Chamorros, but the first European descriptions of the physical appearance of the Chamorro people in the 1520s and '30s report that both sexes had long black hair, which they wore down to their waists or even further. Another description, given about 50 years later, reported that the natives at that time were tying up their hair into one or two topknots.

Chamorro institutions on Guam advocate for the spelling Chamoru, as reflected in the 2017 Guam Public Law 33-236. In 2018, the Commission on the Chamoru Language and the Teaching of the History and Culture of the Indigenous People of Guam announced Chamoru as the preferred standardized spelling of the language and people, as opposed to the conventional spelling Chamorro.

The Chamorro language is included in the Malayo-Polynesian subgroup of the Austronesian family. Because Guam was colonized by Spain for over 300 years, Chamorro has acquired many loanwords from Spanish. An example is how the traditional Chamorro number system was replaced by Spanish numbers.

Chamorro is often spoken in many homes, but this is becoming less common. However, a resurgence of interest in reviving the language has occurred, and all public schools on both Guam and the Northern Marianas are now required by law to teach the Chamorro language as part of the elementary-, middle-, and high-school curriculum.

A commonly spoken phrase in Chamorro is håfa adai, a greeting which approximates "hello" in English.