The Chantry of Andraste is the dominant religion in Ferelden and much of the rest of Thedas. The Chantry is a powerful force in Ferelden, both because they are revered and listened to by those in power and authority for spiritual guidance, and because they have their own religious army: The Templars. The Chantry teaches from the Chant of Light, the collection of Andraste's teachings which have evolved and expanded in their interpretations over time.
One of the most important teachings of the Chant in its influence on the culture and laws of Ferelden is that "Magic exists to serve man, and never to rule over him". The Chantry teaches that the Darkspawn were created when Magisters of the Tevinter Imperium forced their way into the Maker's Golden City (Dragon Age's equivalent of Heaven) and corrupted it turning the city black (the Black City is the one permanent geographical location in The Fade, always visible in the distance) and becoming the first Darkspawn; according to Chantry when the Chant of Light is sung from the four corners of the world the Maker will return to rebuild his Golden City. For this reason the Chantry believes all mages must be controlled; the Templars are tasked with monitoring the Circle of Magi and hunting down apostates (illegal mages who are not part of the Circle). The Chantry teaches that all apostates are maleficarum (mages who use forbidden magics such as blood magic), however many are just mages who wish to live outside of Templar control and away from the Circle. The Chantry includes mages of the Dalish elves in their definition of apostates, thereby forcing them to hide their powers in front of humans, increasing the tension between elves and humans.
Only women are allowed to become ordained priests of the Chantry, but there positions for men such as Templars and other non-ordained positions. The Chantry is led by the Divine from Val Royeaux in Orlais, below her are the Grand Clerics such as the one who leads the Chantry in Ferelden, each chantry is run by a Revered Mother with the assistance of a number of sisters. Orphans are often given to the chantry and raised to be priests or Templars.
The Chantry views all non-humans as in need of saving, and they spread the Chant of Light to them in efforts to convert them. This is not always peaceful such as the Exalted March against the elves of the Dales, which caused the Dales to fall and left the elves homeless.
The Chantry appears to be closely based off Christianity in many of its customs, beliefs and its aesthetics. There many things about the Chantry which mirror Christianity, such as the faith being based on a figure who died and was risen to immortality with God/The Maker. There is also the split in the Chantry's history between the Imperium and The Chantry led by Orlais over the nature of Andraste's divinity; this splits reflects the Christian split between the Orthodox church of Eastern Europe (Tevinter) and the Roman Catholics in the west (Orlais).