The Municipality of L’Isle-aux-Allumettes is located in the province of Quebec. It is nestled within Pontiac MRC in the Outaouais region. The island covers 190,19 km² and is considered the largest island entity along the Ottawa River, with 22 km in length and 12 km in width. At the top of the island (north-west), the river becomes wide, forming the lac des Allumettes, which covers 32 miles in length over an area of 46 square miles.
The northern portion if the island hosts the municipalities of Sheenboro, Chichester and Waltham. The south side is boarded by the province of Ontario.