Biiliac width

Ilium of pelvis
Overview of Ilium as largest region of the pelvis.
Capsule of hip-joint (distended). Posterior aspect. (Ilium labeled at top.)
Details
Identifiers
Latin	Os ilium
MeSH	D007085
TA	A02.5.01.101
FMA	16589
Anatomical terms of bone []

The ilium (/ˈɪliəm/) (plural ilia) is the uppermost and largest part of the hip bone, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.

The ilium of the human is divisible into two parts, the body and the wing; the separation is indicated on the top surface by a curved line, the arcuate line, and on the external surface by the margin of the acetabulum.

The name comes from the Latin (, ilis), meaning "groin" or "flank".

The ilium consists of the body and wing. 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.

The body (Latin: corpus) forms less than two-fifths of the acetabulum; and also forms part of the acetabular fossa. The internal surface of the body is part of the wall of the lesser pelvis and gives origin to some fibers of the obturator internus.

The wing (Latin: ala) is the large expanded portion which bounds the greater pelvis laterally. It has an external and an internal surface, a crest, and two borders—an anterior and a posterior.