São Tomé Day, or Dia de São Tomé, is celebrated annually on December 21 in São Tomé and Príncipe. This day commemorates the arrival of the first Europeans to the island in 1471 and coincides with the feast day of Saint Thomas. The islanders celebrate with music and dancing, marking the cultural significance of the day. São Tomé and Príncipe, located in the Gulf of Guinea, was uninhabited when Portuguese explorers arrived, and it later became a site for sugar plantations worked by enslaved Africans and 'degredados' sent from Portugal. Over time, the islands transitioned to cacao and coffee production, with cacao becoming the main cash crop in the 1890s. The day serves as a reminder of the islands' historical journey and cultural heritage.