The Amsterdam burgomaster and Dutch East India Company director Nicolaes Witsen (1641-1717) compiled an extensive collection of material goods, natural specimens, and an immense visual archive of images, rivalling princely collections outside the Dutch Republic. Witsen’s collection did not exist solely for his personal pleasure nor to supplement his reputation but was used as an ever-developing research tool in Witsen’s endeavours to acquire, distribute, and process information. This dissertation seeks to illuminate how Witsen used his visual archive to supplement his investigations and those of a global network of correspondents. First, it identifies important figures in Witsen’s collecting network and analyzes the epistemological values informing their discussions to determine how Witsen valued and employed images to supplement research pursued alongside his peers, and as tools of eyewitness testimony. Second, I present two case studies based on objects once in his collection, considering their global narratives and how they reflect the variety of functions objects in collections performed in early modern discourse. The first case study examines an album of painted plant studies originating from Batavia (today Jakarta, Indonesia). It analyses the album’s material origins and content and considers how Witsen employed the album and its images to supplement the resources of the Amsterdam Hortus Botanicus. The second case study examines the evidence for painted portraits, now lost, of two men abducted from the island New Guinea, identified by their Dutch-given names Pieter Geel and Jan Craanvogel. It considers how Witsen used images and his reports from his network to investigate the peoples inhabiting New Guinea and the portraits’ function as evidentiary images testifying to Witsen’s authority on the subject by documenting his personal encounter with the two men, also recorded in verbal accounts. This dissertation asserts that images held an authoritative position in Witsen’s collecting and research, functioning ...