Catechism of the Catholic Church §2818 — excerpt
In the Lord's Prayer, "thy kingdom come" refers primarily to the final coming of the reign of God through Christ's return. But, far from distracting the Church from her mission in this present world, this desire commits her to it all the more strongly.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: Roman Missal, Eucharistic Prayer IV, 118