Factor VIII is an essential blood-clotting protein, also known as anti-hemophilic factor. In humans, factor VIII is encoded by the F8 gene. Defects in this gene result in hemophilia A, a recessive X-linked coagulation disorder.

[[Hemophilia type A]] is a rare genetic disorder caused by missing or defective [[factor VIII]] (FVIII), a [[clot]]ting protein in the [[blood]]. The [[disease]] is usually inherited, but in about one-third of known cases, it is caused by a spontaneous [[mutation]].