Celsus was presumably born in Upper Italy, where the name of Iuventius was common and where senatorial Iuventii can also be found. In 106 or 107 Celsus was praetor. In 114/115 he was governor of Thracia, and immediately afterwards, in 115, he became suffect consul. In 129 Celsus held the office of consul the second time and became proconsul of Asia in 129/130.
Celsus succeeded his father Iuventius Celsus in the Proculian school of lawyers. He was part of the Consilium of Hadrian and helped bring about the Senatusconsultum Iuventianum, which held that a good-faith possessor of an inheritance only had to yield it back inasmuch as he was enriched by it. Another dictum of his, impossibilium nulla obligatio est – impossible obligations are void – has become a core tenet of civil law.
Celsus' legal style was bold and biting. He left us the only definition Roman law ever conceived for itself – ius est ars boni et aequi. Pliny the Younger did, hoverer, criticise his rhetorical weaknesses. Celsus' principal work are his 39 libri digestorum.