Portugal was the first European kingdom-state to engage in significant overseas exploration. Beginning in the fifteenth century, Portuguese mariners explored and claimed lands along the west and east coasts of Africa. They also claimed the islands of Cape Verde off the coast of Africa and the Madeiras in the Atlantic.
Vasco da Gama, sailing under the Portuguese flag, reached India in 1498. The Portuguese claimed control of a variety of trade centers within the Indian subcontinent, including the colony of Goa and Calicut. They claimed at various times dozens of the so-called "Spice Islands" in modern Indonesia, including Molucca, which was hotly contested by European nations afterward.
They established a trade presence in China, including the trading depot of Macao, and, in addition to slave and gold trading ports, controlled colonies in Africa that ranged from Mozambique to Angola. Their largest possession was the South American nation of Brazil, the largest Portuguese-speaking nation in the world, and among Portugal's longest-standing colonies. Portugal's presence in Africa and South America would persist until the nineteenth and twentieth centuries.
We should note, as a final point, that many Portuguese mariners sailed under other flags. Ferdinand Magellan, for instance, was Portuguese, but his expedition that circumnavigated the globe was done on behalf of Spain. And many regions, including the African interior, were explored but not claimed by the Portuguese.