Summary: The principal data are collected about the fall and the distribution of the fragments of the Siena, Italy, meteorite (11·6°E., 43·1°N.). A complete individual, weighing 110·55 g, is described in some detail. Crust morphology, mineralogical composition, and structure were studied. Optical data were established by microscopical analysis and both thin and polished sections were observed. Compared with available electron-probe analysis they are found in good agreement. The chemical analysis is Fe 12·93, Ni 1·39, Co 0·09, FeS 5·46, SiO₂ 37·10, TiO₂ 0·14, Al₂O₃ 3·91, FeO 11·46, MnO 0·35, MgO 23·81, CaO 1·63, Na₂O 0·90, K₂O 0·16, P₂O₅ 0·44, H₂O⁺ 0·10, H₂O⁻ 0·00, Cr₂O₃ 0·56, total 100·43. Siena is an ordinary chondrite, with relatively ambiguous characteristics and evident features of recrystallization and metamorphism.