The Macao–Nagasaki connection in the early seventeenth century involved a complex set of interrelationships with regard to trade, mission, cultural intercourse, and other important topics between China, Japan, Portugal, Spain, and the Netherlands. The rise to importance of Macao and Nagasaki was the result of the interruption of Sino–Japanese trade relations and the policy adjustments by the governments of China and Japan to bring the Portuguese under their control and administration. One of the main differences between Macao and Nagasaki was that the former remained a Portuguese settlement for centuries, while the latter was an enclave first of the Portuguese and later of the Dutch. This short article, mainly based on secondary sources by C. R. Boxer, Leonard Blussé, and others, is a tentative study of the international relations in East Asia and their changes after the appearance of the Portuguese and the Dutch in the late sixteenth and early seventeenth centuries.

Two important facts make the sixteen-century international relations in East Asia different from the situation before: the appearance of the Portuguese in this area and the deterioration of Sino–Japanese relations.

For the first thirty years after the Portuguese arrived on the coast of Guangdong in 1514, encounters between them and the Chinese were rife with misunderstandings and conflicts, because Portugal was not a tributary country of China; the Portuguese were totally new to the Chinese. As the Portuguese could not establish formal commercial relations with China, in order to acquire Chinese goods they sought close relations with Chinese and later Japanese smugglers and pirates. They even engaged in the slave trade, which gave them a very bad name in China.