An ice boat (often spelled as "iceboat") is a boat or purpose-built framework similar in functional design to a sail boat but fitted with skis or runners (skates) and designed to run over ice instead of through (liquid) water. Ice yachting is the sport of sailing and racing iceboats. Sailable ice is known in the sport as "hard water" versus sailing on liquid or "soft" water. A related sport, land sailing, utilizes a configuration with an iceboat-like fuselage or frame equipped with wheels instead of runners. Iceboats commonly used for racing are usually only for one person, but several classes of two-seat and multiple-seat iceboats are more or less common. On some boats, a "side car" can be fitted to take others along for a ride.

Traditional iceboats from before the late 19th century were used for transportation of goods and racing. These boats reached lengths of 30 to 50 feet (15 m) and were sometimes transported between sites on rail cars. Ice sailing was first developed in Europe. In America, it was done in several locations where the sport also continues today. Many active ice sailing clubs are thriving in the northern States and Canadian Provinces, including on the Hudson River, Long Island Sound, Detroit, Michigan, Sandusky, Ohio, Gull Lake, Michigan, Lake Muskegon, Michigan, Geneva Lake, Wisconsin, Oshkosh, Wisconsin, Hamilton Bay, Ontario, Ghost Lake, Alberta and on other venues as far south as Decatur and Springfield, Illinois. Some of the older large "stern steerer" iceboats can seat several in their "baskets." Several of these boats are maintained and raced today. The Northwest Ice Yacht Association sponsors an annual regatta that includes classes for these boats. This annual regatta recently celebrated its 100th anniversary.

Ice is water frozen into the solid state. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions. The addition of other materials such as soil may further alter the appearance.

Ice appears in nature in forms of snowflakes, hail, icicles, glaciers, pack ice, and entire polar ice caps. It is an important component of the global climate, and plays an important role in the water cycle. Furthermore, ice has numerous cultural applications, from ice cooling of drinks to winter sports and the art of ice sculpting.

The molecules in solid ice may be arranged in different ways, called phases, depending on the temperature and pressure. Usually ice is the phase known as ice I_h, which is the most abundant of the varying solid phases on the Earth's surface. The most common phase transition to ice I_h occurs when liquid water is cooled below 0°C (273.15K, 32°F) at standard atmospheric pressure. It can also deposit from vapour with no intervening liquid phase, such as in the formation of frost.

A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland (lakes) or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a vessel small enough to be carried aboard another vessel (a ship). Another less restrictive definition is a vessel that can be lifted out of the water. Strictly speaking and uniquely a submarine is a boat as defined by the Royal Navy^{[citation needed]}. Some boats too large for the naval definition include the Great Lakes freighter, riverboat, narrowboat and ferryboat. The term armed boat, used primarily by English speaking naval forces, referred to any boat carrying either a cannon or armed occupants, such as marines^{[citation needed]}.

Boats have served as short-distance transportation since early times. Circumstantial evidence, such as the early settlement of Australia over 40,000 years ago, and findings in Crete dated 130,000 years ago, suggests that boats have been used since ancient times. The earliest boats have been predicted to be logboats. The oldest boats to be found by archaeological excavation are logboats from around 7,000–10,000 years ago. The oldest recovered boat in the world is the Pesse canoe; it is a dugout or hollowed tree trunk from a Pinus sylvestris. It was constructed somewhere between 8200 and 7600 B.C. This canoe is exhibited in the Drents Museum in Assen, Netherlands; other very old dugout boats have been recovered. A 7,000 year-old seagoing boat made from reeds and tar has been found in Kuwait.