Which Byzantine emperor codified Roman law in the Corpus Juris Civilis?

The Byzantine emperor who codified Roman law in the Corpus Juris Civilis was Justinian I. His legal project was one of the most influential achievements of his reign and preserved, reorganised, and transmitted centuries of Roman legal thought.

Justinian ordered the work soon after becoming emperor in AD 527. Officials including the jurist Tribonian reviewed imperial constitutions and earlier legal writings, removing contradictions and obsolete material. The first version of the Codex was issued in 529, while the Digest and Institutes were completed in 533. A revised Codex followed in 534.

The Corpus Juris Civilis contained the Codex, the Digest, and the Institutes; later compilations of Justinian’s subsequent laws, known as the Novellae, are commonly treated as a fourth component. Although the legislation was produced in the Eastern Roman Empire, much of it was written in Latin, the traditional language of Roman government.

A common mix-up is calling the entire work simply the “Code of Justinian.” Strictly speaking, the Code is only one part of the larger Corpus. The collection later shaped Byzantine law, medieval European legal education, canon law, and the civil-law traditions used in many modern countries.