Saint-Léonard is a municipality in the district of Sierre in the canton of Valais in Switzerland. The Saint-Léonard underground lake situated there is a tourist attraction.
Saint-Léonard is first mentioned in 1218 as apud Sanctum Leonardum. The municipality was formerly known by its German name St. Leonhard, however, that name is no longer used.
Saint-Léonard has an area, as of 2009, of 3.9 square kilometers (1.5 sq mi). Of this area, 1.83 km2 (0.71 sq mi) or 46.9% is used for agricultural purposes, while 0.6 km2 (0.23 sq mi) or 15.4% is forested. Of the rest of the land, 1.11 km2 (0.43 sq mi) or 28.5% is settled (buildings or roads), 0.15 km2 (37 acres) or 3.8% is either rivers or lakes and 0.17 km2 (0.066 sq mi) or 4.4% is unproductive land.
Of the built up area, housing and buildings made up 9.7% and transportation infrastructure made up 13.1%. Power and water infrastructure as well as other special developed areas made up 3.3% of the area while parks, green belts and sports fields made up 1.8%. Out of the forested land, 13.8% of the total land area is heavily forested and 1.5% is covered with orchards or small clusters of trees. Of the agricultural land, 5.6% is used for growing crops and 4.6% is pastures, while 36.7% is used for orchards or vine crops. All the water in the municipality is flowing water. Of the unproductive areas, 2.8% is unproductive vegetation and 1.5% is too rocky for vegetation.
The municipality is located in the Sierre district. The original haufendorf village (an irregular, unplanned and quite closely packed village, built around a central square) was located on the left side of the Lienne and along the right side of the Rhone valley. By the middle of the 20th Century, it had spread out into the valley floor