Zeolites (microporous aluminosilicates) and related molecular sieves have found wide application as catalysts, sorbents and ion-exchange materials. New zeolites with large pores are much in demand1-4, and have been sought for several decades4-7. All known zeolites, both natural and synthetic, contain pores comprised of 12 or fewer tetrahedrally coordinated silicon or aluminium atoms (T-atoms), but several microporous aluminophosphates with wider pores are now known2,8-12. The practical value of these large-pore phosphate-based materials is limited, however, by their poor thermal and hydrothermal stability. Here we report the synthesis of a high-silica zeolite with pores comprised of 14 T-atoms. Preliminary data indicate that this thermally stable large-pore material exhibits the kind of strong acidity that makes other zeolites useful catalysts.