"The kingdom of God is at hand"
"Now after John was arrested, Jesus came into Galilee, preaching the gospel of God, and saying: 'The time is fulfilled, and the kingdom of God is at hand: repent, and believe in the gospel.'" "To carry out the will of the Father Christ inaugurated the kingdom of heaven on earth." Now the Father's will is "to raise up men to share in his own divine life". He does this by gathering men around his Son Jesus Christ. This gathering is the Church, "on earth the seed and beginning of that kingdoms".
Source: Catechism of the Catholic Church (Vatican.va)