Volcanic glass from the seventeenth century bc (c. 3600 bp) Minoan eruption of Santorini (Thera) has been recovered from a 4 cm thick tephra deposit at Gölhisar Gölü, a small lake in SW Turkey. Analysis of single grains of this glass by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) provides, for the first time, an accurate determination of the trace element composition of the juvenile glass component of this eruption, free from contaminants such as phenocrysts or detrital material. Individual glass shards (>150 μm) show a large degree of variation in their trace element composition, indicative of substantial, small-scale compositional heterogeneity in the magma. This is a result of the proximity of crystallizing phases, and provides insights into the chemical evolution of the Minoan magma. The range of elemental compositions displayed by individual glass shards combined with the consistency of many trace element ratios are characteristics of the Minoan glass. These features provide a trace element signature for the Minoan tephra, which will be of value in stratigraphic correlation across the Eastern Mediterranean.