Marcus Julius Agrippa I (c. 11 BC – c. AD 44), also known as Agrippa I (Hebrew: אגריפס, epithet Agrippa the Great) or Herod Agrippa, was a Roman citizen, under the patronage of Antonia Minor, friend of Roman emperors Caligula and Claudius, and the last client king of Judea (r. 41–44). He was a grandson of Herod the Great and Mariamne I, and he was the father of Herod Agrippa II, the last king from the Hasmonean branch of the Herodian dynasty. He played crucial roles in Roman politics under Caligula and was a "kingmaker" of Claudius. In return he was rewarded with the kingship of Judea, which brought a brief period of relative independence to Judea and significant influence in the Eastern portion of the Roman Empire.
He spent his childhood and youth at the imperial court in Rome, where he befriended the imperial princes Claudius and Drusus. He suffered a period of disgrace following the death of Drusus, which forced him to return to Judea. Back in Rome around 35, Tiberius made him the guardian of his grandson Tiberius Gemellus, and Agrippa approached the other designated heir, Caligula. The ascent of Caligula to the throne allowed Agrippa to become king of Batanea, Trachonitis, Gaulanitis, Auranitis, Paneas and Iturea in 37 by obtaining the old tetrarchies of Philip and Lysanias, then Galilee and Perea in 40 following the disgrace of his uncle, Herod Antipas.
After the assassination of Caligula, he played an important role in Rome to the accession of Claudius to becoming the head of the empire in 41, and he was endowed with the former territories of Herod Archelaus (Idumea, Judea and Samaria) thus ruling over a territory as vast as the kingdom of Herod the Great.
Carrying a dual Jewish and Roman identity, he played the role of intercessor on behalf of the Jews with the Roman authorities and, on the domestic level, gave hope to some of his Jewish subjects of the restoration of an independent kingdom. Pursuing the Herodian policy of euergetism through major works in several Greek cities of the Near East, he nevertheless alienated some of his Greek and Syrian subjects while his regional ambitions earned him the opposition of Marsus, the legate of Roman Syria.
Agrippa I died suddenly from an “infestation of worms” in 44. In a Christian context, he is traditionally identified as the king simply named Herod whose death is recounted in Acts 12 (12:20–23).