The figure of Santa Claus dates back to a 3rd century Greek monk known as St. Nicholas. He became the patron saint of children and is said to bring gifts to children on his saint's day, which falls on December 6.
The historical figure of St. Nicholas does not resemble Santa Claus. He is usually depicted as a tall, thin man in long robes. St. Nicholas earned his sainthood through refusing to renounce Christianity, his charity, and the miracles he supposedly performed. He became a very popular saint, presiding over the well-being of sailors and children. Traditionally, he brought gifts on December 6. However, after the protestant reformation, some regions began to exchange gifts on Christmas, telling their children that the gifts came from the Christ child. The practice of exchanging gifts on Christmas slowly spread throughout Europe.
The name "Santa Claus" comes from "Sinterklaas," a Dutch nickname for St. Nicholas. When Dutch immigrants came to America, they brought their traditions with them, and Sinterklaas slowly morphed into the modern Santa Claus.
Much of the modern mythology around Santa Claus stems from 19th century American stories and poems, such as "The Night Before Christmas." These depictions also became popular in Europe.
In many European cultures, Saint Nicholas does not travel alone. In most of Germany, he has an assistant named Knecht Ruprecht, a sooty figure who carries the gifts for good children and beats naughty children with a rod. In the Netherlands, a similar figure goes by Zwarte Piet. In Austria and Southern Germany, he has a terrifying assistant called Krampus, a devil-like creature.