Why do Catholics pray to Mary?

Catholics do not pray to Mary as they pray to God. Rather, they ask for her intercession — requesting that she pray to God on their behalf, just as you might ask a friend to pray for you. The difference is that Mary, as the Mother of God and one who is fully in God's presence, is a uniquely effective intercessor. This practice is rooted in Scripture: at the Wedding at Cana (John 2:1-11), Mary interceded with Jesus and He performed His first miracle. The Hail Mary is largely biblical — 'Hail, full of grace' comes from the angel Gabriel (Luke 1:28), and 'Blessed are you among women' from Elizabeth (Luke 1:42). Catholic teaching holds that honoring Mary ultimately glorifies God, since all her grace comes from Him.