Essex was an American whaler from Nantucket, Massachusetts, which was launched in 1799. In 1820, while at sea in the southern Pacific Ocean under the command of Captain George Pollard Jr., the ship was attacked and sunk by a sperm whale. Thousands of miles from the coast of South America with little food and water, the 20-man crew was forced to make for land in the ship's surviving whaleboats.

The men suffered severe dehydration, starvation, and exposure on the open ocean, and the survivors eventually resorted to eating the bodies of the crewmen who had died. When that proved insufficient, members of the crew drew lots to determine whom they would sacrifice so that the others could live. Seven crew members were cannibalized before the last of the eight survivors were rescued, more than three months after the sinking of the Essex. First mate Owen Chase and cabin boy Thomas Nickerson later wrote accounts of the ordeal. The tragedy attracted international attention, and inspired Herman Melville to write his famous 1851 novel Moby-Dick.

The sperm whale or cachalot (Physeter macrocephalus) is the largest of the toothed whales and the largest toothed predator. It is the only living member of the genus Physeter and one of three extant species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale of the genus Kogia.

The sperm whale is a pelagic mammal with a worldwide range, and will migrate seasonally for feeding and breeding. Females and young males live together in groups, while mature males (bulls) live solitary lives outside of the mating season. The females cooperate to protect and nurse their young. Females give birth every four to twenty years, and care for the calves for more than a decade. A mature sperm whale has few natural predators, although calves and weakened adults are sometimes killed by pods of killer whales (orcas).

Mature males average 16 metres (52 ft) in length but some may reach 20.7 metres (68 ft), with the head representing up to one-third of the animal's length. Plunging to 2,250 metres (7,382 ft), it is the third deepest diving mammal, exceeded only by the southern elephant seal and Cuvier's beaked whale. The sperm whale uses echolocation and vocalization as loud as 230 decibels (re 1 µPa m) underwater. It has the largest brain on Earth, more than five times heavier than a human's. Sperm whales can live 70 years or more.Spermaceti (sperm oil), from which the whale derives its name, was a prime target of the whaling industry, and was sought after for use in oil lamps, lubricants, and candles. Ambergris, a solid waxy waste product sometimes present in its digestive system, is still highly valued as a fixative in perfumes, among other uses. Beachcombers look out for ambergris as flotsam. Sperm whaling was a major industry in the 19th century, depicted in the novel Moby-Dick. The species is protected by the International Whaling Commission moratorium, and is listed as vulnerable by the International Union for Conservation of Nature.