Dutch (endonym: Nederlands [ˈneːdərlɑnts] ^ⓘ, Nederlandse taal) is a West Germanic language of the Indo-European language family, spoken by about 25 million people as a first language and 5 million as a second language and is the third most spoken Germanic language. In Europe, Dutch is the native language of most of the population of the Netherlands and Flanders (which includes 60% of the population of Belgium). Dutch was one of the official languages of South Africa until 1925, when it was replaced by Afrikaans, a separate but partially mutually intelligible daughter language of Dutch. Afrikaans, depending on the definition used, may be considered a sister language, spoken, to some degree, by at least 16 million people, mainly in South Africa and Namibia, and evolving from Cape Dutch dialects.

In South America, Dutch is the native language of the majority of the population of Suriname, and spoken as a second or third language in the multilingual Caribbean island countries of Aruba, Curaçao and Sint Maarten. All these countries have recognised Dutch as one of their official languages, and are involved in one way or another in the Dutch Language Union. The Dutch Caribbean municipalities (St. Eustatius, Saba and Bonaire) have Dutch as one of the official languages. In Asia, Dutch was used in the Dutch East Indies (now mostly Indonesia) by a limited educated elite of around 2% of the total population, including over 1 million indigenous Indonesians, until it was banned in 1957, but the ban was lifted afterwards. About a fifth of the Indonesian language can be traced to Dutch, including many loan words. Indonesia's Civil Code has not been officially translated, and the original Dutch language version dating from colonial times remains the authoritative version. Up to half a million native speakers reside in the United States, Canada and Australia combined, and historical linguistic minorities on the verge of extinction remain in parts of France and Germany.

Dutch is one of the closest relatives of both German and English, and is colloquially said to be "roughly in between" them. Dutch, like English, has not undergone the High German consonant shift, does not use Germanic umlaut as a grammatical marker, has largely abandoned the use of the subjunctive, and has levelled much of its morphology, including most of its case system. Features shared with German, however, include the survival of two to three grammatical genders – albeit with few grammatical consequences – as well as the use of modal particles, final-obstruent devoicing, and (similar) word order. Dutch vocabulary is mostly Germanic; it incorporates slightly more Romance loans than German, but far fewer than English.

In Belgium, the Netherlands and Suriname, the native official name for Dutch is Nederlands (historically Nederlandsch before the Dutch orthographic reforms). Sometimes Vlaams ("Flemish") is used as well to describe Standard Dutch in Flanders, whereas Hollands ("Hollandic") is occasionally used as a colloquial term for the standard language in the central and northwestern parts of the Netherlands.

English uses the adjective Dutch as a noun for the language of the Netherlands and Flanders. The word is derived from Proto-Germanic *þiudiskaz. The stem of this word, *þeudō, meant "people" in Proto-Germanic, and *-iskaz was an adjective-forming suffix, of which -ish is the Modern English form. Theodiscus was its Latinised form and used as an adjective referring to the Germanic vernaculars of the Early Middle Ages. In this sense, it meant "the language of the common people". The term was used as opposed to Latin, the non-native language of writing and the Catholic Church. It was first recorded in 786, when the Bishop of Ostia writes to Pope Adrian I about a synod taking place in Corbridge, England, where the decisions are being written down "tam Latine quam theodisce" meaning "in Latin as well as common vernacular".

According to a hypothesis by De Grauwe, In northern West Francia (i.e. modern-day Belgium) the term would take on a new meaning during the Early Middle Ages, when, within the context of a highly dichromatic linguistic landscape, it came to be the antonym of *walhisk (Romance-speakers, specifically Old French). The word, now rendered as dietsc (Southwestern variant) or duutsc (Central and Northern Variant), could refer to the Dutch language itself, as well as a broader Germanic category depending on context. During the High Middle Ages "Dietsc/Duutsc" was increasingly used as an umbrella term for the specific Germanic dialects spoken in the Low Countries, its meaning being largely implicitly provided by the regional orientation of medieval Dutch society: apart from the higher echelons of the clergy and nobility, mobility was largely static and hence while "Dutch" could by extension also be used in its earlier sense, referring to what today would be called Germanic dialects as opposed to Romance dialects, in many cases it was understood or meant to refer to the language now known as Dutch.

In the Low Countries Dietsch or its early modern Dutch form Duytsch as an endonym for Dutch gradually went out of common use and was gradually replaced by the Dutch endonym Nederlands. This designation (first attested in 1482) started at the Burgundian court in the 15th century, although the use of neder, laag, bas, and inferior ("nether" or "low") to refer to the area known as the Low Countries goes back further in time, with the Romans referring to the region as Germania Inferior ("Lower" Germania). It is a reference to the Low Countries' downriver location at the Rhine–Meuse–Scheldt delta near the North Sea.

From 1551, the designation Nederlands received strong competition from the name Nederduytsch (literally "Low Dutch", Dutch being used in its archaic sense covering all continental West Germanic languages). It is a calque of the aforementioned Roman province Germania Inferior and an attempt by early Dutch grammarians to give their language more prestige by linking it to Roman times. Likewise, Hoogduits ("High German") and Overlands ("Upper-landish") came into use as a Dutch exonym for the various German dialects used in neighboring German states. Use of Nederduytsch was popular in the 16th century but ultimately lost out over Nederlands during the close of the 18th century, with (Hoog)Duytsch establishing itself as the Dutch exonym for German during this same period.