Description.

Single or cespitose, leaves glaucous gray or green up to 25-45 x 8-24 cm, broadly linear to ovate, short-acuminate, thick rigid, plane to slightly hollowed above, rounded below, sometimes slightly narrowed toward base with bud-printing. The margin usually corneous, dark brown with slender reddish brown teeth, frequently down-flexed, 1-2 cm apart. Terminal spine black to grey, 2-3 cm long, grooved above. Up to 12 umbels of yellow flowers on the top quarter of a 2-3 m tall stem .

Agave sebastiana is closely related to A. shawii.

Agave sebastiana is found on East San Benito Island in the Cedros group.