In the English language, the word nigger is an ethnic slur used against black people, especially African Americans. Starting in the 1980s, references to nigger have been progressively replaced by the euphemism "the N-word", notably in cases where nigger is mentioned but not directly used. In an instance of linguistic reappropriation, the term nigger is also used casually and fraternally among African Americans, most commonly in the form of nigga, whose spelling originated from the phonological system of African-American English.

The word nigger, then spelled in English neger or niger, appeared in the 16th century as an adaptation of French nègre, itself from Spanish negro. They go back to the Latin adjective niger ([ˈnɪɡɛr]), meaning "black". It was initially seen as a relatively neutral term, essentially synonymous with the English word negro. Rather than demonstrating a hostile meaning of the word itself, early attested uses during the Atlantic slave trade (16th–19th century) often conveyed a patronizing tone that reflects the underlying attitudes held towards black people by their white authors. Building up on these mildly disparaging social meanings, the word took on a derogatory connotation from the mid-18th century onward, to the extent that it had "degenerated into an overt slur" by the middle of the 19th century. Some authors kept on using the term in a neutral sense up until the later part of the 20th century, at which point the use of nigger became increasingly seen as controversial regardless of its context or intent.

Because the word nigger has historically "wreaked symbolic violence, often accompanied by physical violence", it began to disappear from general popular culture from the second part of the 20th century onward, at the exception of cases derived from intra-group usage such as hip hop culture. The Merriam-Webster Online Dictionary describes the term as "perhaps the most offensive and inflammatory racial slur in English". The Oxford English Dictionary writes that "this word is one of the most controversial in English, and is liable to be considered offensive or taboo in almost all contexts (even when used as a self-description)". Intra-group usage has been criticized by some contemporary African-American authors, a group of them (the eradicationists) calling for the total abandonment of its usage (even under the variant nigga), which they see as contributing to the "construction of an identity founded on self-hate". In wider society, the inclusion of the word nigger in classic works of literature (as in Mark Twain's 1884 book The Adventures of Huckleberry Finn) and in more recent cultural productions (such as Quentin Tarantino's 1994 film Pulp Fiction) has sparked controversy and ongoing debate.

By extension of its derogatory connotation, the word nigger has also been historically used to designate "any person considered to be of low social status" (as in the expression white nigger) or "any person whose behaviour is regarded as reprehensible", and in other national contexts to refer to Aboriginal and Māori people. In some cases, with awareness of the word's offensive connotation, but without intention to cause offense, it can refer to a "a victim of prejudice likened to that endured by African Americans" (as in John Lennon's 1972 song "Woman Is the Nigger of the World").