The Lisbon Regicide or Regicide of 1908 was the assassination of King Carlos I of Portugal and the Algarves and his heir-apparent, Luís Filipe, Prince Royal of Portugal, by assassins sympathetic to Republican interests and aided by elements within the Portuguese Carbonária, disenchanted politicians and anti-monarchists. The events occurred on 1 February 1908 at the Praça do Comércio along the banks of the Tagus River in Lisbon, commonly referred to by its antiquated name Terreiro do Paço.

Dom Carlos I, known as the Diplomat, the Martyr, and the Oceanographer, among many other names, was King of Portugal from 1889 until his assassination in 1908. He was the first Portuguese king to die a violent death since King Sebastian in 1578.