Malay seals are defined in this study as 'seals from Southeast Asia with inscriptions at least partially in the Jawi/Arabic script or the Malay language'. Malay seals originate from the present-day territories of Malaysia, Brunei, Singapore, Indonesia and the southern parts of Thailand and the Philippines. They are found primarily as seal impressions stamped in lampblack, ink or wax on manuscript letters, treaties and other documents, but some seal matrices have also been documented. Just over 1500 Malay seals have been recorded, dating from the early 17th to the early 20th century, and are presented in the accompanying catalogue. Malay seals have never been studied before, despite their enormous value as historical sources, and this thesis is the first study of the sigillography of the Malay world. As small but highly visible and symbolic emblems of their users, seals were designed to portray the image of the self that the sealholder wished to project, but were also no less strongly shaped by the prevailing social, political, religious and artistic norms of their time. It is these multifarious layers of identity, both consciously and subconsciously revealed in seals, that this study attempts to identify, record and interpret. An introductory chapter surveys the use of seals in the Malay world prior to the earliest surviving Malay seals, on the basis of archaeological evidence and textual sources. The core of the thesis is a critical analysis of the seal inscriptions according to their constituent elements: introductory formulae, names and titles, pedigrees, place namesireligious legends and talismanic elements. On the basis of this study, Malay seal inscriptions can be characterised as self-consciously Islamic compositions, which seek to depict the sealholder in the most sophisticated and formal Arabic-Islamic terms, yet whose Malay identity is never in doubt. In an epilogue, the seals are re-evaluated from a chronological viewpoint, in an investigation into the origins and development of the Malay seal tradition. The conclusion reached is that Malay seals were probably first used in the early Muslim kingdoms of north Sumatra, at least by the 14th century, but may have been introduced further east in the archipelago as late as the early 17th century.