Lughnasadh is a Gaelic holiday celebrated on August 1. Some Irish people continue to celebrate the holiday popularly with fires and dancing. Lughnasadh is also the modern Gaelic term for the month of August.

In neopaganism, Lughnasadh (also spelled Lunasa, Lughnasadh, or Lughnasa) is one of the eight sabbatss or solar festivals in the Wheel of the Year. It is the first of the three autumn harvest festivals, the other two being Mabon and Samhain. It commemorates the sacrifice and death of the Corn God; in its cycle of death, nurturing the people, and rebirth, the corn is thought of as an aspect of the Sun God, Whom the Gaels called Lugh.

The name Lammas is also used, taken from an Anglo-Saxon and Christianized holiday occurring at the same time, that may or may not have a common origin. As the name (from hlaf-mass, "loaves festival") implies, it is a feast of thanksgiving for bread, symbolizing the first fruits of the harvest.

Some Pagans mark the holiday by baking a figure of the God in bread, and then symbolically sacrificing and eating it.

Among the sabbats, Lughnasadh is preceded by Midsummer and followed by Mabon.