The 5 October 1910 Revolution (Portuguese: Revolução de 5 de outubro de 1910) was the overthrow of the centuries-old Portuguese monarchy and its replacement by the First Portuguese Republic. It was the result of a coup d'état organized by the Portuguese Republican Party.
By 1910, the Kingdom of Portugal was in deep crisis: national anger over the 1890 British Ultimatum, the royal family's expenses, the assassination of the King and his heir in 1908, changing religious and social views, instability of the two political parties (Progressive and Regenerator), the dictatorship of João Franco, and the regime's apparent inability to adapt to modern times all led to widespread resentment against the Monarchy. The proponents of the republic, particularly the Republican Party, found ways to take advantage of the situation. The Republican Party presented itself as the only one with a programme capable of regaining Portugal's lost status and placing it on the path of progress.
