The Andalusian dialects of Spanish (Spanish: andaluz, pronounced [andaˈluθ], locally [andaˈluh, ændæˈlʊ]) are spoken in Andalusia, Ceuta, Melilla, and Gibraltar. They include perhaps the most distinct of the southern variants of peninsular Spanish, differing in many respects from northern varieties in a number of phonological, morphological and lexical features. Many of these are innovations which, spreading from Andalusia, failed to reach the higher strata of Toledo and Madrid speech and become part of the Peninsular norm of standard Spanish. Andalusian Spanish has historically been stigmatized at a national level, though this appears to have changed in recent decades, and there is evidence that the speech of Seville or the norma sevillana enjoys high prestige within Western Andalusia.

Due to the large population of Andalusia, Andalusian dialects are among the most widely spoken dialects in Spain. Within the Iberian Peninsula, other southern varieties of Spanish share some core elements of Andalusian, mainly in terms of phonetics  – notably Extremaduran Spanish and Murcian Spanish as well as, to a lesser degree, Manchegan Spanish.

Due to massive emigration from Andalusia to the Spanish colonies in the Americas and elsewhere, all Latin American Spanish dialects share some fundamental characteristics with Western Andalusian Spanish, such as the use of ustedes instead of vosotros for the second person informal plural, seseo, and a lack of leísmo. Much of Latin American Spanish shares some other Andalusian characteristics too, such as yeísmo, weakening of syllable-final /s/, pronunciation of historical /x/ or the ⟨j⟩ sound as a glottal fricative, and merging syllable-final /r/ and /l/. Canarian Spanish is also strongly similar to Western Andalusian Spanish due to its settlement history.

Most Spanish dialects in Spain differentiate, at least in pre-vocalic position, between the sounds represented in traditional spelling by ⟨z⟩ and ⟨c⟩ (before ⟨e⟩ and ⟨i⟩), pronounced [θ], and that of ⟨s⟩, pronounced [s]. However, in many areas of Andalusia, the two phonemes are not distinguished and /s/ is used for both, which is known as seseo /seˈseo/. In other areas, the sound manifests as [s̟] (a sound close, but not identical to [θ]), which is known as ceceo (/θeˈθeo/). Unless a specific dialect is transcribed, transcriptions in this article follow the standard pattern found in the syllable onset, so that the orthographic ⟨z⟩ and the soft ⟨c⟩ are transcribed with ⟨θ⟩, whereas the orthographic ⟨s⟩ is transcribed with ⟨s⟩. Additionally, in most regions of Andalusia which distinguish /s/ and /θ/, the distinction involves a laminal [s], as opposed to the apico-alveolar [s̠] of most of Spain.

The pronunciation of these sounds in Andalusia differs geographically, socially, and among individual speakers, and there has also been some shift in favor of the standard distinción. As testament to the prevalence of intra-speaker variation, Dalbor (1980) found that many Andalusians alternate between a variety of sibilants, with little discernible pattern. Additionally, the idea that areas of rural Andalusia at one time exclusively used ceceo has been challenged, and many speakers described as ceceante or ceceo-using have in fact alternated between use of [s̟] and [s] with little pattern. While ceceo is stigmatized and usually associated with rural areas, it is worth noting that it was historically found in some large cities such as Huelva and Cádiz, although not in the more prestigious cities of Seville and Córdoba.

Above all in eastern Andalusia, but also in locations in western Andalusia such as Huelva, Jerez, and Seville, there is a shift towards distinción. Higher rates of distinción are associated with education, youth, urban areas, and monitored speech. The strong influence of media and school may be driving this shift.

Penny (2000) provides a map showing the different ways of pronouncing these sounds in different parts of Andalusia. The map's information almost entirely corresponds to the results from the Linguistic Atlas of the Iberian Peninsula, realized in the early 1930s in Andalusia and also described in Navarro Tomás, Espinosa & Rodríguez-Castellano (1933). These sources generally highlight the most common pronunciation, in colloquial speech, in a given locality.

According to Penny (2000), the distinction between a laminal /s/ and /θ/ is native to most of Almería, eastern Granada, most of Jaén, and northern Huelva, while the distinction between an apical /s/ and /θ/, as found in the rest of Peninsular Spanish, is native to the very northeastern regions of Almería, Granada and Jaén, to northern Córdoba, not including the provincial capital, and to a small region of northern Huelva. Also according to Penny (2000) and Navarro Tomás, Espinosa & Rodríguez-Castellano (1933), seseo predominates in much of northwestern Huelva, the city of Seville as well as northern Seville province, most of southern Córdoba, including the capital, and parts of Jaén, far western Granada, very northern Málaga, and the city of Almería. Likewise, ceceo is found in southern Huelva, most of Seville, including an area surrounding but not including the capital, all of Cádiz including the capital, most of Málaga, western Granada, and parts of southern Almería.