Portuguese-Spanish relations are closely aligned with one another, underpinned by shared membership of the Ibero-American Summit, Council of Europe, European Union, Eurozone, Schengen Area and NATO, and make up the vast majority of the Iberian Peninsula and Macaronesia.

After the Umayyad conquest of the Iberian Peninsula, a long process of reconquest (in Portuguese and Spanish: Reconquista) began.

An attempt to unite all Iberian medieval kingdoms failed with the death, in 1500, of Miguel da Paz, Prince of Portugal, Asturias, Girona and Viana.

As a result of the 1494 Treaty of Tordesillas, Portugal acquired its most potentially important colony, Brazil (much of the South American continent), as well as a number of possessions in Africa and Asia, while Castile took the rest of South America and much of the North American continent as well as a number of possessions in Africa, Oceania, and Asia as the important colony of the Philippines.

Henry also lacked heirs and his death triggered a succession crisis, where the main claimants to the throne were Philip II of Spain and Anthony, Prior of Crato.

The Portuguese, courtesy of their long-standing alliance, aligned themselves with Great Britain, while Spain, through the Pacte de Famille, allied themselves to France.

The War of the Oranges (Portuguese: Guerra das Laranjas; French: Guerre des Oranges; Spanish: Guerra de las Naranjas) was a brief conflict in 1801 in which Spanish forces, instigated by the government of France, and ultimately supported by the French military, invaded Portugal.

It was a precursor to the Peninsular Wars, resulting in the Treaty of Badajoz, the loss of Portuguese territory, in particular Olivenza, as well as ultimately setting the stage for the complete invasion of the Iberian Peninsula by Spanish and French forces.

In 1807, the king of Spain and his French allies invaded Portugal successfully and unusually quickly, using a route that crossed through Spanish territory.

Both lost their American colonies shortly after the end of the Peninsular War, which severely weakened their global power.

In 1936, Francisco Franco launched a coup against the Spanish government and after three years of civil war, his nationalists were triumphant.

Despite this, Spain, alike Portugal, still were opposed to the Soviet-led Warsaw Pact considered communist and left-wing movements threatened their regimes.

[2] The two states gave independence to their former colonies, liberalized their economies and began the process of applying for membership of the European Economic Community.

[5] The same year, both countries also held a solemn border opening ceremony, which had been closed due to the COVID-19 pandemic crisis.

[8] They also signed agreements relative to fish & game in the international river border of the Miño and to the launch of a Statute of the Cross-Border Worker.

Olivenza had been under continuous Portuguese sovereignty since prior to 1297 when it was occupied by Spain in 1801 and formally ceded by Portugal later that year by the Treaty of Badajoz.

Spain objects on the basis that the Savage Islands do not have a separate continental shelf,[10] according to the article 121[11] of the United Nations Convention on the Law of the Sea.