This article introduces the special issue on 'Material Encounters' by addressing the praxis of materiality across time, disciplines, areas of study, and technologies. We use the metonyms of track and trace and the distinction of objects and things to disentangle ways in which materials and understandings of the material mediate dynamic encounters with specific people or places, particularly in Oceania. These material encounters generate diverse, unstable forms of knowing on all sides, through the uneven flux of human embodiment (in encounters) and embodied materialization (in object, inscription, representation, memorialization). We juxtapose the assumed, if increasingly challenged priority of materials in object-oriented fields such as archaeology and museology; the reflective revival of material culture studies and the 'material turn' in anthropology from around 1990; and the belated recognition of the salience of materials and materialities by historians, whose craft depends on present material traces of the pasts they seek to elucidate. With reference to the agency of persons, places, time, or things, we stress the plurality of materialities and their related ontologies, and the qualities of movement, instability, and incompletion inherent in all encounters.