Treaty of Windsor (1386)

For other treaties called "Treaty of Windsor", see Treaty of Windsor.

Treaty of Windsor

Treaty of peace, friendship and confederation between John I of Portugal and Richard II, King of England
Treaty of Windsor
Drafted	9 May 1386
Signed	24 February 1387
Location	Westminster
Negotiators	Fernando Afonso de Albuquerque Lourenço João Fogaça Richard d'Alberbury John Clanowe Richard Ronhale
Signatories	Kingdom of England Kingdom of Portugal
Ratifiers	Richard II of England
Depositary	Portuguese National Archives
Language	Latin

Marriage of John I, King of Portugal and Philippa of Lancaster, daughter of John of Gaunt, 1st Duke of Lancaster.

The Treaty of Windsor is a diplomatic alliance signed between Portugal and England on 9 May 1386 in Windsor and sealed by the marriage of King John I of Portugal (House of Aviz) to Philippa of Lancaster, daughter of John of Gaunt, 1st Duke of Lancaster. With the victory at the Battle of Aljubarrota, assisted by English archers, John I was recognised as the undisputed King of Portugal, putting an end to the interregnum of the 1383–1385 Crisis. The Treaty of Windsor established a pact of mutual support between the countries.

This document is preserved at the Portuguese National Archives.

Historian Matthew Winslett says, "This treaty has been the cornerstone of both nations' relations with each other ever since."

Enduring to this day, the Treaty of Windsor holds the record as the longest-lasting diplomatic treaty in recorded history.

See also

• Anglo-Portuguese Treaty of 1373
• British Ultimatum of 1890 – British diplomatic ultimatum to Portugal regarding Portugal's claims in AfricaPages displaying short descriptions of redirect targets
• Timeline of Portuguese history
• Anglo-Portuguese Alliance – 1386 alliance between the UK and Portugal
• Treaty of Tagilde – Anglo-Portuguese treaty signed in 1372
• Operation Alacrity

Bibliography

• Country profile of Portugal, Archived 31 July 2003 at the Wayback Machine Foreign, Commonwealth and Development Office website
• Livermore, H.V (1947). A History of Portugal. Cambridge University Press. p. 179. Retrieved 7 October 2021.
• Winslett, Matthew (August 2008). The Nadir of Alliance: The British Ultimatum of 1890 and Its Place in Anglo-Portuguese Relations, 1147–1945 (PDF) (MA). Supervising Professor: Douglas Richmond. The University of Texas at Arlington. p. 14. Archived from the original on 17 September 2008. Retrieved 7 October 2021.