The Preslav Treasure is one of the most important jewellery hoards of the Middle Ages and comprises over 180 pieces of jewellery and appliques, coins, and spoons, made from gold, silver, precious stones, pearls and enamels. The treasure was unearthed in 1978 near the town of Preslav in Bulgaria, which was the capital of the First Bulgarian State (681-1018) from the late ninth century to 971. The objects cast a light on the relations between medieval Bulgaria and its neighbour Byzantium: most of the valuable pieces would have come from Constantinople, perhaps on the occasion of the marriage between the Bulgarian Tsar Peter I (927-969) and the Byzantine princess Marie-Irene in 927. For the first time since its excavation, the Preslav Treasure has been subject to scientific analyses, conducted in the Leibniz-Zentrum für Archäologie Mainz, with a restoration and photographic documentation. This book comprises fourteen papers presented during the conference organised in collaboration with Musée du Louvre, Paris, in 2018.