The Roman–Sassanid war of 421–422 is a conflict between the Eastern Roman Empire and the Sassanids.

The casus belli is the persecution of Christians by the Sassanid king Bahram V, which had come as a response to attacks by Christians against Zoroastrian temples; the Christian Eastern Roman Emperor Theodosius II declares war and obtains some victories, but in the end the two powers agree to sign a peace on the status quo ante.