Saint Nicholas Day, or the Feast of Saint Nicholas, is observed on 6 December or on the evening of 5 December in Western Christian nations, and on 19 December in Eastern Christian countries using the old church Calendar.

A 4th century bishop of Myra in Roman Greece noted for his generosity, Saint Nicholas has become the patron saint of Russia and Greece, of sailors and children, and the inspiration for Santa Claus.

Most commonly observed with Mass in Catholic churches and special services in Protestant congregations, Saint Nicholas Day is also observed by children placing shoes in the foyer before bedtime in the hope of finding coins in the soles come morning.