in Christianity, the spiritual realm over which God reigns as king, or the fulfillment on Earth of God's will. The phrase occurs frequently in the New Testament, primarily used by Jesus Christ in the first three Gospels. It is generally considered to be the central theme of Jesus' teaching, but widely differing views have been held about Jesus' teaching on the Kingdom of God and its relation to the developed view of the church.

Though the phrase itself rarely occurs in pre-Christian Jewish literature, the idea of God as king was fundamental to Judaism, and Jewish ideas on the subject undoubtedly underlie, and to some extent determine, the New Testament usage. Behind the Greek word for kingdom (basileia) lies the Aramaic term malkut, which Jesus may have used. Malkut refers primarily not to a geographical area or realm nor to the people inhabiting the realm but, rather, to the activity of the king himself, his exercise of sovereign power. The idea might better be conveyed in English by an expression such as kingship, rule, or sovereignty.

To most Jews of Jesus' time the world seemed so completely alienated from God that nothing would deal with the situation short of direct divine intervention on a cosmic scale. The details were variously conceived, but it was widely expected that God would send a supernatural, or supernaturally endowed, intermediary (the messiah or Son of Man), whose functions would include a judgment to decide who was worthy to “inherit the Kingdom,” an expression which emphasizes that the Kingdom was thought of as a divine gift, not a human achievement.

According to the first three Gospels, most of Jesus' miraculous actions are to be understood as prophetic symbols of the coming of the Kingdom, and his teaching was concerned with the right response to the crisis of its coming. The nationalistic tone of much of the Jewish expectation is absent from the teaching of Jesus.

Scholarly opinion is divided on the question as to whether Jesus taught that the Kingdom had actually arrived during his lifetime. Possibly, he recognized in his ministry the signs of its imminence, but he nevertheless looked to the future for its arrival “with power.” He may well have regarded his own death as the providential condition of its full establishment. Nevertheless, he seems to have expected the final consummation in a relatively short time (Mark 9:1). Thus, Christians were perplexed when the end of the world did not occur within a generation, as Paul, for example, expected. Christian experience soon suggested, however, that, as the result of Christ's Resurrection, many of the blessings traditionally reserved until the life of the age to come were already accessible to the believer in this age. Thus, though the phrase Kingdom of God was used with decreasing frequency, that for which it stood was thought of as partly realized here and now in the life of the church, which at various periods has been virtually identified with the Kingdom; the Kingdom of God, however, would be fully realized only after the end of the world and the accompanying Last Judgment. The Johannine writings in the New Testament played a large part in the transition to this traditional Christian understanding of the Kingdom of God.