The St Sixte Catholic Church, established in 1885, was in the village of Saint Sixtus, north of Thurso, in the Outaouais.
It housed a municipal office, still provided church services, and had recently been renovated.
The flames spread quickly but no one was hurt, according to Roch Lafortune, a man who lives next to the church.
The fire started in a house adjacent to the church, then spread into the church itself, Lafortune said.
Firefighters in the village called on neighbouring municipalities to send reinforcements, including Gatineau firefighters.
The cause of the blaze is under investigation.