Lac la Martre is the third largest lake in the Northwest Territories, covering an area of approximately 1,687 km². The lake is roughly 55 miles in length and is notably shallow, with a maximum depth of around 30 feet. It sits within the Tłı̨chǫ region of the Northwest Territories and drains via the La Martre River, which flows from the lake's outlet. The lake's waters are described as crystal clear.

Access to the lake is primarily by floatplane from Yellowknife, with a flight time of approximately 50 to 55 minutes. There is no road access, making this a genuinely remote destination. The established lodge on the lake is situated on Clemy Island, near the middle of the lake. Non-motorized watercraft, including canoes, are available for use at the lodge facility on Clemy Island.

The lake is known for trophy northern pike and lake trout (namaycush). Pike fishing is particularly noted in early season when fish can be spotted in the shallow, clear water. Wind can be a significant factor on the lake, with gusts reaching 40 kilometres per hour or more, which can make boat handling and paddling challenging, particularly in open bays.

The lake falls within the traditional territory of the Tłı̨chǫ people, who have inhabited and worked this land since time immemorial. The surrounding landscape is described as scenic boreal wilderness. The Aurora Borealis is visible in the area from early September onward, making autumn a notable time to visit. The lake also experiences extended daylight during summer months, consistent with its subarctic latitude. The broader watershed connects to features including Saddle Lake, Mazenod Lake, Bea Lake, and Hislop Lake, with the La Martre River eventually joining the Marian River drainage system leading toward the North Arm of Great Slave Lake.