Approximate area of Rioplatense Spanish with Patagonian variants included.
Rioplatense Spanish (eɪ/; Spanish: español rioplatense, locally castellano rioplatense) is a dialect of the Spanish language spoken mainly in the areas in and around the Río de la Plata Basin of Argentina and Uruguay. It is also referred to as River Plate Spanish or Argentine Spanish. Being the most prominent dialect to employ voseo in both speech and writing, many features of Rioplatense are also shared with the varieties spoken in Eastern Bolivia, Chile, and Peru. This dialect is often spoken with an intonation resembling that of the Neapolitan language of Southern Italy, but there are exceptions. The usual word employed to name the Spanish language in this region is castellano (English: Castilian) and seldom español (English: Spanish). See names given to the Spanish language.
Due to the fact that Rioplatense is merely a peculiar dialect and not a language, there are no credible figures for a total number of speakers. Generally, native speakers of Spanish who were raised in Uruguay or the majority of Argentina are assumed to speak Rioplatense (at least informally) just as, for instance, Americans would be assumed to speak American English, rather than any other variety of English. The total population of these areas would amount to some 25–30 million, depending on the definition and expanse.
Rioplatense is mainly based in the cities of Buenos Aires, Rosario, Santa Fe, La Plata, Mar del Plata and Bahía Blanca in Argentina, and Montevideo in Uruguay, the most populated cities in the dialectal area, along with their respective suburbs and the areas in between. This regional form of Spanish is also found in other areas, not geographically close but culturally influenced by those population centers (e.g., in parts of Paraguay and in all of Patagonia). Rioplatense is the standard in audiovisual media in Argentina and Uruguay. To the north, and northeast exists the hybrid Riverense Portuñol.