Architectonica maxima, common name giant sundial, is a species of sea snail, a marine gastropod mollusk in the family Architectonicidae, which are known as the staircase shells or sundials. Occurs in the Indo-Pacific: from East Africa, including Madagascar, to the Red Sea and the Persian Gulf, down to the Philippines and on to Polynesia. Distributed in the north, to Japan, and to Hawaii in the east; and to the south and east of Australia, in Queensland.