Portugal is a small country of just 92,000 square kilometres – approximately the size of Hungary, a little larger than Austria or marginally smaller than Greece. It occupies less than one sixth of the Iberian peninsula's land surface. On any map of that peninsula, it has the appearance of a neat rectangle, extending for some 560 kilometres from north to south and up to 215 kilometres from west to east. Such compactness, and such symmetry, suggest internal coherence. However, while this is an impression that carries some validity it requires considerable qualification.

For much of its history Portugal was a remote frontier outpost, far from the European centre of gravity. On its northern and eastern flanks lay what would eventually be Spain – the country's only, and overweening, direct neighbour. Close by to the south loomed Africa – for long both a danger and a temptation – while to the west stretched vast expanses of open Atlantic. Thus, clinging to the southwestern extremity of Europe, Portugal was separated from everywhere on the continent except Spain; but its inhabitants nevertheless possessed, thanks to their long Atlantic coastline, the opportunity to make counterbalancing contacts across the sea. In effect, Portugal was closely hemmed in by Spain, Africa and the Atlantic – and each exerted its own profound influence on Portuguese history.

There are no obvious geographical reasons why Portugal should be distinct from the rest of the Iberian peninsula.