Architectonica maxima, the 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.

[1] Architectonica maxima has a shell that reaches 19–82 mm[2] and it is the largest member of the sundial family.

The shoulder slope is divided into two ribs by a spiral groove.

This species can be found in the Indo-Pacific, from East Africa and the Persian Gulf to western Pacific, Japan, eastern Australia, New Zealand, New Caledonia and Hawaii.

[2][4][5][3] Giant sundial is a carnivore deeper water sea snail living on sandy patches and muddy sublittoral bottoms,[3] close to soft corals, at a depth of 10 – 280 m.[5]