脑炎（Encephalitis），一种急性脑部的炎症，通常由病毒感染造成。

病患症状包括发烧、头痛、呕吐、意识混乱、疲倦、嗜睡和畏光。 严重的症状包括癫痫、颤抖（tremors）、幻觉、记忆问题。幼儿可能会食欲不佳或燥动不安。

Encephalitis (from Ancient Greek ἐγκέφαλος, enképhalos "brain", composed of ἐν, en, "in" and κεφαλή, kephalé, "head", and the medical suffix -itis "inflammation") is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue. Further symptoms include seizures or convulsions, tremors, hallucinations, stroke, and memory problems. In 2013, encephalitis was estimated to have resulted in 77,000 deaths, down from 92,000 in 1990.