Sark (Sercquiais: Sèr or Cerq) is a part of the Channel Islands in the southwestern English Channel, off the coast of Normandy, France. It is a royal fief, which forms part of the Bailiwick of Guernsey, with its own set of laws based on Norman law and its own parliament. It has a population of about 500. Sark (including the nearby island of Brecqhou) has an area of . Little Sark is a peninsula joined by a natural but high and very narrow isthmus to the rest of Sark Island.
Sark is one of the few remaining places in the world where cars are banned from roads and only tractors, bicycles and horse-drawn vehicles are allowed. In 2011, Sark was designated as a Dark Sky Community and the first Dark Sky Island in the world.
Sark consists of two main parts, Greater Sark, located at about , and Little Sark to the south. They are connected by a narrow isthmus called La Coupée which is long and has a drop of on each side. Protective railings were added in 1900; before then, children would crawl across on their hands and knees to avoid being blown over the edge. A narrow concrete road covering the entirety of the isthmus was built in 1945 by German prisoners of war under the direction of the Royal Engineers. Due to its isolation, the inhabitants of Little Sark had their own distinct form of Sercquiais, the native Norman dialect of the island.
The highest point on Sark is above sea level. A windmill, dated 1571, is found there, the sails of which were removed during World War II. This high point is named Le Moulin, after the windmill. The location is also the highest point in the Bailiwick of Guernsey. Little Sark had a number of mines accessing a source of galena. At Port Gorey, the ruins of silver mines may be seen. Off the south end of Little Sark are the Venus Pool and the Adonis Pool, both natural swimming pools whose waters are refreshed at high tide.
The whole island is extensively penetrated at sea level by natural cave formations that provide unique habitats for many marine creatures, notably sea anemones, some of which are only safely accessible at low tide.