Celticism may refer to:
- A word or linguistic property adapted from a Celtic language
- List of English words of Celtic origin
- List of English words of Scottish Gaelic origin
- Irish words used in the English language
- List of English words of Irish origin
- List of English words of Welsh origin
- Hiberno-English
- Kiltartanese
- Political pan-Celticism
- The ideology of Lega Nord which culturally identifies with the Celtic people
- The romanticist Celtic Revival
- Celts (modern), a modern Celtic identity that has emerged in Western Europe since the 18th century
- Celtism also known as Celtic neopaganism
- Celticisation, the historic process of conquering and assimilating by the ancient Celts