The Anglo‑Portuguese Alliance, first formalised in a treaty of 1373, is the oldest diplomatic alliance still in effect, a long‑standing pact between the Kingdom of Portugal and the Kingdom of England that has been reaffirmed across centuries and political changes.
Origin
The original agreement, often referred to as the Treaty of 1373, established perpetual friendship and mutual support between the two kingdoms, creating a diplomatic framework that outlived medieval politics and was reinforced by later treaties and declarations across subsequent centuries.
Historical reinforcement
The alliance was reinforced at key moments in history, including later formal agreements such as the Treaty of Windsor and periodic diplomatic recognitions, and it remained a reference point for Anglo‑Portuguese relations through dynastic, military and colonial periods.
Modern recognition
The alliance continues to be celebrated in modern diplomatic practice and commemorated by official ceremonies and exchanges, with both governments describing it as the world’s longest standing alliance and marking milestone anniversaries in contemporary foreign‑office statements.
Significance
Its longevity illustrates how long‑term strategic interests, maritime cooperation and shared diplomatic commitments can produce durable international ties, and it remains a symbolic and practical element of relations between Portugal and the United Kingdom today.
Quick related facts
- Founding treaty: 1373.
- Also reinforced by: Treaty of Windsor and later agreements.
- Status: widely recognised as the oldest active diplomatic alliance.
- Modern commemoration: celebrated in official UK and Portuguese statements.