Some think the Church today is the Kingdom of God. Although there is a connection between the two, they are not identical. Jesus Christ is the Head of the Church (Ephesians 1:22 Ephesians 1:22And has put all things under his feet, and gave him to be the head over all things to the church,
American King James Version×), which is the body of believers called by God now to proclaim the good news of the coming Kingdom of God.
Christ rules His Church, thus it is under His royal power. We might say the Church is the forerunner of the coming Kingdom of God. Or, as Jesus Christ said, the Kingdom of God is like the proverbial mustard seed, waiting to grow rapidly at Jesus' return (Matthew 13:31-32 Matthew 13:31-32  Another parable put he forth to them, saying, The kingdom of heaven is like to a grain of mustard seed, which a man took, and sowed in his field:
 Which indeed is the least of all seeds: but when it is grown, it is the greatest among herbs, and becomes a tree, so that the birds of the air come and lodge in the branches thereof.
American King James Version×).
The Bible, however, doesn’t use the word kingdom to apply directly to the Church. Instead, the Kingdom of God refers to God's prophesied government, which will literally rule this on this earth (Revelation 11:15 Revelation 11:15And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.
American King James Version×; Revelation 5:10). The Kingdom of God is not here yet.