The diaphragma sellae or sellar diaphragm is a small, circular sheet of dura mater forming an (incomplete) roof over the sella turcica and covering the pituitary gland lodged therein.

The opening formed by the diaphragma sellae varies greatly in size between individuals.

[1] Pituitary tumours may grow to extend superiorly beyond the diaphragma sellae.

[1] Violation of the diaphragma sellae during an endoscopic endonasal transsphenoidal pituitary tumor resection will result in a cerebrospinal fluid leak.

[citation needed] This article incorporates text in the public domain from page 814 of the 20th edition of Gray's Anatomy (1918)