Omoo: A Narrative of Adventures in the South Seas is the second book by American writer Herman Melville, first published in London in 1847, and a sequel to his first South Seas narrative Typee, also based on the author's experiences in the South Pacific. After leaving the island of Nuku Hiva, the main character ships aboard a whaling vessel that makes its way to Tahiti, after which there is a mutiny and a third of the crew are imprisoned on Tahiti. In 1949, the narrative was adapted into the exploitation film Omoo-Omoo, the Shark God.

The basis for the book are the author's experiences in the South Seas. According to scholars Harrison Hayford and Walter Blair, in August and September 1842, the Lucy Ann, an Australian whaleship, took Melville from the Marquesas Islands to Tahiti. There the crew revolted. After being imprisoned in the native jail, he strolled around the islands for some days, before embarking on another whaler for a voyage of six months.

In the Preface to Omoo, Melville claimed the book was autobiographical, written "from simple recollection" of some of his experiences in the Pacific in the 1840s and strengthened by his retelling the story many times before family and friends. But scholar Charles Roberts Anderson, working in the late 1930s, discovered that Melville had not simply relied on his memory and went on to reveal a wealth of other sources he drew on in writing the book.

Later, Melville scholar Harrison Hayford made a detailed study of these sources and, in the introduction to a 1969 edition of Omoo, summed up the author's practice, showing that this was a repetition of a process previously used in Typee:

"He had altered facts and dates, elaborated events, assimilated foreign materials, invented episodes, and dramatized the printed experiences of others as his own. He had not plagiarized, merely, for he had always rewritten and nearly always improved the passages he appropriated.....first writing out the narrative based on his recollections and invention, then using source books to pad out the chapters he had already written and to supply the stuff of new chapters that he inserted at various points in the manuscript."

To a greater extent than he did in Typee, Melville used several source books from which he took passages and rewrote them for his book. The most important of these source books are William Ellis, Polynesian Researches from 1833, George H. von Langsdorff, Voyages and Travels in Various Parts of the World from 1813, Charles S. Stewart, A Visit to the South Seas in the U.S. ship Vincennes from 1831, and Charles Wilkes, Narrative of the United States Exploring Expedition of 1845.

In 1842, the narrator, having just escaped an "indulgent captivity" among the natives of Nuku Hiva, joins the crew of an Australian whaling ship from Sydney. He does not give his name, but one crew member calls him "Typee". Soon after coming aboard he meets and forms a friendship with the vessel's surgeon, a tall thin man known to his crew-mates as "Dr Long Ghost".

Compared to Typee, in Omoo a new style was emerging, of a "distinct and original signature," as critic Warner Berthoff describes it. Biographer Hershel Parker finds the narrator "powerfully attractive," because through the comical nature of the events "a new sensibility was emerging." Melville's "new command of language," as Parker calls this development, came with hints of what would be characteristic of his mature style in Moby-Dick and later books. These include the merging of images from various historical times and places. Essentially, an example of this can be found in chapter 27 of Omoo, where the narrator sees on a ship in the harbor of Tahiti the name of a town along the Hudson river: "In an instant, palm-trees and elms--canoes and skiffs--church spires and bamboos--all mingled in one vision of the present and the past."