Lake St. Moritz (German: St. Moritzersee, Romansh: Lej da San Murezzan) is a lake near St. Moritz, Switzerland. With a surface of 0.78 kmē, it is smaller than the main lakes of the Upper Engadin valley (Lake Sils, Lake Silvaplana).
Every January or early February, Polo matches are held on the lake. Compared to polo played in the summer, a slightly larger and lighter red ball is used that is easily visible in the snow.
For three weekends every February, horse races are held on the frozen lake. This races called "White Turf" are held since 1907 and brings the wealthy tourists to the lake for champagne and betting. This is also the location, where sports enthusiasts invented the sport of skijoring. In this type of race, thoroughbred horses compete without riders on their backs, but instead skiers in tow. While the sport is also played in other alpine countries, it still is mainly found in the region in which it as originated.