Sinustrombus sinuatus, common name the laciniate conch, is a species of sea snail, a marine gastropod mollusc in the true conch family, Strombidae. It is native to the tropical Indo-Pacific region.
The shell of S. sinuatus is thick and solid with a large body whorl. The maximum length is 13 cm (5 in), but a more common size is 10 cm (4 in). The short spire consists of about twelve whorls; the exterior of the shell is white, blotched or spotted with yellow, orange or light tan, and the interior is brown, purple or pink. It is rather varied in morphology, with the lip of the aperture having a number of blunt finger-like processes, which vary from being almost unnoticeable to being prominent. The difference in shape of these variations is larger than the difference between the shape of this mollusc and the related species Lambis millepeda, Lambis scorpius and Lambis lambis, which it resembles.