Cogne parish is dedicated to Sant’Orso, a clergyman from Aosta Valley who lived between the 7th and 8th centuries and who was renowned for his thaumaturgic powers. Legend goes that it was he himself who reclaimed the land of Cogne, which previously had been inhospitable. In reality the canons from Sant’Orso collegiate church of Aosta, to which the parish appears to have belonged since 1184, could have played an important role in this sense. The canons of Sant’Orso owned the parish until 1820, when the ownership went on to the bishop.
In 1642 the church was consecrated by monsignor Vercellin. During that time the building acquired its present appearance after the extension works it went through. The inside is made up of a single nave with a rectangular ground-plan and a presbytery with an octagonal dome. It still preserves some valuable 18th century altars, made of gold-painted carved wood and helical columns. The bell-tower was built in 1840 after the previous one, which had been renovated in 1828, was knocked down because of stability and height problems.