: ilia) is the uppermost and largest region of the coxal bone, and appears in most vertebrates including mammals and birds, but not bony fish.

Together with the ischium and pubis, to which the ilium is connected, these form the pelvic bone, with only a faint line indicating the place of union.

In humans, biiliac width is an anatomical term referring to the widest measure of the pelvis between the outer edges of the upper iliac bones.

[4] The clade Dinosauria is divided into the Saurischia and Ornithischia based on hip structure, including importantly that of the ilium.

The acetabulum, which can be thought of as a "hip-socket", is an opening on each side of the pelvic girdle formed where the ischium, ilium, and pubis all meet, and into which the head of the femur inserts.

The orientation and position of the acetabulum is one of the main morphological traits that caused dinosaurs to walk in an upright posture with their legs directly underneath their bodies.

[7] Ile in classical Latin can refer to the flank of the body,[8] or to the groin,[8] or the part of the abdomen from the lowest ribs to the pubes.

[8] Troy is referred to in classical Latin as Ilium,[8] Ilion[8] or Ilios[17] and in ancient Greek as Ἴλιον[9] or Ἴλιος.

[9] The first editions of the official Latin nomenclature, Nomina Anatomica of the first 80 years (first in 1895) used the Vesalian expression os ilium.