Saint Martin's Day or Martinmas, sometimes historically called Old Halloween or Old Hallowmas Eve, is the feast day of Saint Martin of Tours and is celebrated in the liturgical year on 11 November. In the Middle Ages and early modern period, it was an important festival in many parts of Europe, particularly Germanic-speaking regions. In these regions, it marked the end of the harvest season and beginning of winter. and the "winter revelling season". Traditions include feasting on 'Martinmas goose' or 'Martinmas beef', drinking the first wine of the season, and mumming. In some German and Dutch-speaking towns, there are processions of children with lanterns (Laternelaufen), sometimes led by a horseman representing St Martin. The saint was also said to bestow gifts on children. In the Rhineland, it is also marked by lighting bonfires.

Martin of Tours (died 397) was a Roman soldier who was baptized as an adult and became a bishop in Gaul. He is best known for the tale whereby he cut his cloak in half with his sword, to give half to a beggar who was dressed in only rags in the depth of winter. That night Martin had a vision of Jesus Christ wearing the half-cloak.