The 1909 Benavente earthquake occurred on 23 April at 17:39:36 local in the Santarém District of the Central Region, Portugal.

The estimated moment magnitude 6.0–6.3 earthquake had a maximum Mercalli intensity of IX (Violent).

[2] The northeast-trending Lower Tagus Valley of mainland Portugal covers a 3,200 km2 (1,200 sq mi) area and extends to Lisbon at its southern end.

The first documented earthquake in the region was on 26 January 1531, estimated at Mw  6.9, which caused serious damage in Lisbon and killed two percent of the population.

The study of potentially active faults beneath the valley is obstructed by a thick sedimentary layer especially along the Tagus River's eastern bank.

This suggests the earthquake rupture along the seismogenic structure near the surface were distributed along branch faults or dipped at very shallow angles.