In geometry, a hendecagram (also endecagram or endekagram) is a star polygon that has eleven vertices.

The hendeca- prefix derives from Greek ἕνδεκα (ἕν + δέκα, one + ten) meaning "eleven".

[4] However, Hilton & Pedersen (1986) describe folding patterns for making the hendecagrams {11/3}, {11/4}, and {11/5} out of strips of paper.

[7] The Topkapı Scroll contains images of an 11-pointed star Girih form used in Islamic art.

This design provided more surface area and greater thrust in the earlier part of a launch, and a slower burn rate and reduced thrust after the points of the star were burned away, at approximately the same time as the rocket passed the sound barrier.