A ship is a large vessel that travels in the world's oceans and other sufficiently deep waterways, carrying passengers or cargo, or supporting special missions such as defence, research and fishing. Historically, "ship" is a sailing ship with at least three square masts and full bowsprits. Ships are usually distinguished from ships by size, shape and carrying capacity.

Ships are important contributors to human migration and commerce. They supported colonization and the spread of the slave trade, but also met scientific, cultural and humanitarian needs. After the 16th century, the new works that passed in and out of America through European seamen greatly promoted the growth of world population. Shipping is the largest part of world trade.

As of 2016, there are more than 49000 commercial ships with a total capacity of nearly 1.8 billion tons. Among them, 28% are tankers, 43% are bulk carriers and 13% are container ships. The army operates ships for naval warfare and transports and supports troops on shore. As of 2016, the North Korean people's navy has the largest number of surface ships (967), followed by the Chinese people's Liberation Army Navy (714), the United States Navy (415), the Islamic Republic of Iran Navy (398) and the Russian Navy (352) among the 104 navies in the world. According to various sources, the top 50 naval median fleet has 88 surface ships each.