In Roman Catholic theology, the beatific vision is the direct perception of God enjoyed by those who are in Heaven, imparting supreme happiness or blessedness.

"How great will your glory and happiness be, to be allowed to see God, to be honored with sharing the joy of salvation and eternal light with Christ your Lord and God... to delight in the joy of immortality in the Kingdom of Heaven with the righteous and God's friends" ~ St. Cyprian

More specifically, Catholic Encyclopedia defines it as such:

The immediate knowledge of God which the angelic spirits and the souls of the just enjoy in Heaven. It is called "vision" to distinguish it from the mediate knowledge of God which the human mind may attain in the present life. And since in beholding God face to face the created intelligence finds perfect happiness, the vision is termed "beatific".

In Catholic theology, the intercession of saints is valid because those who have died in the faith are with God in Heaven and enjoy the Beatific Vision, i.e., unmediated access to God's presence.

In the papacy of Pope John XXII (1316 - 1334), there was a controversy about when the Beatific Vision occurs. The usual view at the time was that the faithful departed would experience it after death. However, Pope John argued for a time in some sermons that those who had died would not experience the Beatific Vision until the Last Judgment, though he never proclaimed this ex cathedra. A consistory was held in January 1334, and Pope John backed away from his novel views to the more standard understanding.