进行性多灶性白质脑病（英语：Progressive multifocal leukoencephalopathy，PML），或称进行性多灶性脑白质炎，是一种以进行性脑损伤和多灶性脑白质炎症为特点的罕见并致命的病毒性疾病。 本病几乎发生于严重的免疫缺陷患者，例如接受免疫抑制药物的器官移植患者，接受特定化疗药物的患者，接受那他珠单抗（一种单克隆抗体，用于治疗多发性硬化）的患者，长期使用依法利珠单抗治疗银屑病的患者，使用brentuximab（Raptiva）治疗霍奇金淋巴瘤的患者，以及艾滋病患者。

进行性多灶性白质脑病是由JC病毒感染所导致。在免疫力正常的人群中JC病毒感染能够被免疫系统所控制，而免疫缺陷病人往往不能抵抗JC病毒的侵袭。

Progressive multifocal leukoencephalopathy (PML) is a rare and usually fatal viral disease characterized by progressive damage (-pathy) or inflammation of the white matter (leuko-) of the brain (-encephalo-) at multiple locations (multifocal). It is caused by the JC virus, which is normally present and kept under control by the immune system. JC virus is harmless except in cases of weakened immune systems. In general, PML has a mortality rate of 30–50 percent in the first few months and those who survive can be left with varying degrees of neurological disabilities.