A whaler or whaling ship is a specialized vessel, designed or adapted for whaling: the catching or processing of whales.

Whaling is the hunting of whales for their usable products such as meat and blubber, which can be turned into a type of oil that was important in the Industrial Revolution. Whaling was practiced as an organized industry as early as 875 AD. By the 16th century, it had become the principal industry in the Basque coastal regions of Spain and France. The whaling industry spread throughout the world and became very profitable in terms of trade and resources. Some regions of the world's oceans, along the animals' migration routes, had a particularly dense whale population and became targets for large concentrations of whaling ships, and the industry continued to grow well into the 20th century. The depletion of some whale species to near extinction led to the banning of whaling in many countries by 1969 and to an international cessation of whaling as an industry in the late 1980s.