The 1531 Lisbon earthquake occurred in the Kingdom of Portugal on the morning of 26 January 1531, between 4 and 5 o'clock. The earthquake and subsequent tsunami resulted in approximately 30,000 deaths. Despite its severity, the disaster was not widely documented until the rediscovery of contemporary records in the early 20th century.

The Tagus is the longest river in the Iberian Peninsula. The river rises in the Montes Universales near Teruel, in mid-eastern Spain, flows 1,007 km (626 mi), generally westward, and empties into the Atlantic Ocean in Lisbon.