May I Use “Mary” as My Baptismal Name?

You may certainly use “Mary” as your baptismal name, as she is the Mother of God and Queen of Heaven and Earth and thus of all angels and saints (see CCC 966). If you don’t want to formally/legally change your name by taking an explicitly Christian name at baptism, you could instead take “Mary” as your Confirmation name and thereby make the Blessed Mother your special patron.