Romance language spoken in Portugal, Brazil, and Portuguese colonial and formerly colonial territories. Galician, spoken in northwestern Spain, is a dialect of Portuguese. Written materials in Portuguese date from a property agreement of the late 12th century, and literary works appeared in the 13th and 14th centuries. In 2008 the Portuguese parliament passed an act mandating the use of a standardized orthography based on Brazilian forms.

Standard Portuguese is based on the dialect of Lisbon. Dialectal variation within the country is not great, but Brazilian Portuguese varies from European Portuguese in several respects, including several sound changes and some differences in verb conjugation and syntax; for example, object pronouns occur before the verb in Brazilian Portuguese, as in Spanish, but after the verb in standard Portuguese. The four major dialect groups of Portuguese are Northern Portuguese, or Galician, Central Portuguese, Southern Portuguese (including the dialect of Lisbon), and Insular Portuguese (including Brazilian and Madeiran). Portuguese is often mutually intelligible with Spanish (Spanish language) despite differences in phonology, grammar, and vocabulary.

Typical of the Portuguese sound system is the use of nasal vowels, indicated in the orthography by m or n following the vowel (e.g., sim “yes,” bem “well”) or by the use of a tilde (∼) over the vowel (mão “hand,” nação “nation”). In grammar its verb system is quite different from that of Spanish. Portuguese has a conjugated or personal infinitive and a future subjunctive and uses the verb ter (Latin tenere, Spanish tener “to have, to hold”) as an auxiliary verb instead of haver (Latin habere, Spanish haber “to have”; in Spanish used only as an auxiliary verb).