Gaelicization or Gaelicisation is the act or process of making something Gaelic, or gaining characteristics of the Gaels. The Gaels are an ethno-linguistic group who are traditionally viewed as having spread from Ireland to Scotland and the Isle of Man. "Gaelic" as a linguistic term, refers to the Gaelic language, but can also refer to the transmission of any other Gaelic cultural feature such as social norms and customs, music, sport etc.
Historically, Gaelicisation was a "natural" process, and was the famous fate of the Picts, many of the Hiberno-Normans and Scoto-Normans, and perhaps most famously of all, the people who became known as the Norse-Gaels. Today, Gaelicisation is more often a pro active or deliberate process, particularly present in Ireland, whereby placenames, surnames and given names are Gaelicised, or more often, re-Gaelicised, in order to prevent the further decline of the modern language.