Willem Verstegen (c. 1612 – 1659) was a merchant in service of the Dutch East India Company and chief trader of factory in Dejima.
Willem Verstegen was born around 1612 in Flushing, Netherlands. In 1629, he completed his apprenticeship, and following a short stay in Batavia, he was sent to Japan in 1632. There he was first employed at the factory (trading post) in Firando (present-day Hirado, Nagasaki). In 1633, he became factor and was assigned to Dejima, where he met several other Hollanders who were survivors of the shipwrecked galleon De Liefde. They had remained there since 1609 and were trading independently. The most prominent among them was Melchior van Santvoort, who had married a Japanese women and with whom he begot a daughter. Not long after arriving in Dejima, Verstegen asked Santvoort's daughter to marry him.
In 1635, he was appointed to the position of trader. On December 7 of that year, Verstegen wrote to Governor Antonie van Diemen that he had learned of some Japan's islands (at around the 37th parallel north) where almost everything was made of gold and silver. This report of the gold and silver islands so captured their imagination that two expeditions were later outfitted in order to find the islands.
In 1639, all Japanese wives with European husbands were ordered by the Shogun to leave the country along with their children. So, Willem Verstegen married Santvoort's daughter on Formosa on their way to Batavia. After their arrival, an expedition under command of Matthijs Quast was outfitted to search the gold and silver islands, but was unsuccessful and abandoned the search. A second expedition led by Maarten Gerritsz Vries and Hendrick Cornelisz Schaep departed in 1643. Schaep and nine of his crew were taken prisoner in Yamada when they tried to supply their ship with fresh water.