Neuritis () is inflammation of a nerve or the general inflammation of the peripheral nervous system. Inflammation, and frequently concomitant demyelination, cause impaired transmission of neural signals and leads to aberrant nerve function. Neuritis is often conflated with neuropathy, a broad term describing any disease process which affects the peripheral nervous system. However, neuropathies may be due to either inflammatory or non-inflammatory causes, and the term encompasses any form of damage, degeneration, or dysfunction, while neuritis refers specifically to the inflammatory process.

As inflammation is a common reaction to biological insult, many conditions may present with features of neuritis. Common causes include autoimmune diseases, such as multiple sclerosis; infection, either bacterial, such as leprosy, or viral, such as varicella zoster; post-infectious immune reactions, such as Guillain-Barré syndrome; or a response to physical injury, as frequently seen in sciatica.

While any nerve in the body may undergo inflammation, specific etiologies may preferentially affect specific nerves. The nature of symptoms depends on the specific nerves involved, neuritis in a sensory nerve may cause pain, paresthesia (pins-and-needles), hypoesthesia (numbness), and anesthesia, and neuritis in a motor nerve may cause paresis (weakness), fasiculation, paralysis, or muscle wasting.

Treatment of neuritis centers around removing or managing any inciting cause of inflammation, followed by supportive care and anti-inflammatory or immune modulatory treatments as well as symptomatic management.