Saint Pierre and Miquelon is an archipelago of eight islands, Saint-Pierre (26 km2 or 10 sq mi) and Miquelon-Langlade (total 216 km2 or 83 sq mi) being the major ones. Collectively the area of the islands is 242 km² (93.4 sq mi). The total coastline is 120 kilometres (75 mi) long.
The island of Saint-Pierre is surrounded to the south-east by smaller dependencies, Petit Colombier, Île aux Marins, Île aux Pigeons and Île aux Vainqueurs, and Grand Colombier to the north. Some of these have been previously inhabited at one time or another, but none are permanently inhabited anymore.
St. Pierre is separated from Miquelon by a 6 kilometres (3.2 nmi) strait with very fierce currents. Fishermen call this section of ocean "The Mouth of Hell". The waters around these islands are very treacherous, and there have been over 600 shipwrecks along the coasts of the islands.
The island(s) of Miquelon-Langlade consists of three formerly separate islands, Miquelon (110 km2 or 42 sq mi), Langlade (91 km2 or 35 sq mi) and Le Cap. In the 18th century an isthmus of sand formed naturally between Miquelon and Langlade. The isthmus was reinforced by hand with sand and quaternary deposits to what is now an 13 kilometres (8.1 mi) sand dune. Local legend says that the entire isthmus was built around the over 500 wrecks that took place in the area. While the ships using that channel between the islands began to get stranded there and certainly contributed to the formation of the isthmus, the legend may be exaggerated. What was originally the island Miquelon is now also called Grande Miquelon while Petite Miquelon refers to Langlade
The climate is very damp and windy, and winters are harsh and long. The spring and early summer are foggy and cool. Late summer and early fall are sunny.
Seals and other wildlife can be found in the Grand Barachois lagoon of Miquelon. Every spring, whales migrating to Greenland are visible off the coasts of Miquelon and St Pierre.
Trilobite fossils have been found on Langlade. There were a number of stone pillars off the island coasts called "L'anse aux Soldats" that have been eroded away and disappeared in the 1970s.