干扰素伽玛（干扰素-γ, Interferon-γ,IFNG、IFNγ）是水溶性二聚体的细胞因子 。是II型干扰素的唯一成员。最初叫巨噬细胞活化因子。

干扰素伽玛蛋白的单体是由六个α螺旋组成一个核心和在C端区延伸展开的片断串行。

生物活性的二聚体是由两个反平行相互锁定的单体形成。

Interferon gamma (IFNγ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock as a product of human leukocytes stimulated with phytohemagglutinin, and by others as a product of antigen-stimulated lymphocytes or tuberculin-sensitized mouse peritoneal lymphocytes challenged with PPD; the resulting supernatants were shown to inhibit growth of vesicular stomatitis virus. Those reports also contained the basic observation underlying the now widely employed interferon gamma release assay used to test for tuberculosis. In humans, the IFNγ protein is encoded by the IFNG gene.