Inflammation of the meninges and brain, generally secondary to an infectious cause. pathogens may be bacterial, viral, fungal, or protozoan.

Meningoencephalitis (; from Ancient Greek: μῆνιγξ, romanized: meninx, lit. 'membrane'; Ancient Greek: ἐγκέφαλος, romanized: enképhalos, lit. 'brain'; and the medical suffix -itis, "inflammation"), also known as herpes meningoencephalitis, is a medical condition that simultaneously resembles both meningitis, which is an infection or inflammation of the meninges, and encephalitis, which is an infection or inflammation of the brain tissue..