Glaucostegus, also known as giant guitarfishes, is a genus of large Indo-Pacific rays, with a single species, Glaucostegus cemiculus, in the East Atlantic, and Mediterranean. They were formerly classified in the family Rhinobatidae but are now recognized as a distinct family, Glaucostegidae.

Their upperparts are uniform pale yellowish, brownish or greyish, and the nose is pale. Most are large, reaching 1.7–3 m (5.6–9.8 ft) in length depending on the exact species involved, except for the small G. obtusus that is less than 1 m (3.3 ft).

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