Pictish is the extinct Brittonic language spoken by the Picts, the people of eastern and northern Scotland from Late Antiquity to the Early Middle Ages. Virtually no direct attestations of Pictish remain, short of a limited number of geographical and personal names found on monuments and the contemporary records in the area controlled by the kingdoms of the Picts, dating to the early medieval period. Such evidence, however, points strongly to the language being an Insular Celtic language related to the Brittonic language spoken prior to Anglo-Saxon settlement in what is now southern Scotland, England, and Wales.

The prevailing view in the second half of the 20th century was that Pictish was a non-Indo-European language isolate, predating a Gaelic colonisation of Scotland or that a non-Indo-European Pictish and Brittonic Pictish language coexisted.

Pictish was replaced by – or subsumed into – Gaelic in the latter centuries of the Pictish period. During the reign of Domnall mac Causantín (889–900), outsiders began to refer to the region as the kingdom of Alba rather than the kingdom of the Picts. However, the Pictish language did not disappear suddenly. A process of Gaelicisation (which may have begun generations earlier) was clearly underway during the reigns of Domnall and his successors. By a certain point, probably during the 11th century, all the inhabitants of Alba had become fully Gaelicised Scots, and the Pictish identity was forgotten.