Two Years Before the Mast is a memoir by the American author Richard Henry Dana Jr., published in 1840, having been written after a two-year sea voyage from Boston to California on a merchant ship starting in 1834. A film adaptation under the same name was released in 1946.

Richard Henry Dana Jr. (August 1, 1815 – January 6, 1882) was an American lawyer and politician from Massachusetts, a descendant of an eminent colonial family, who gained renown as the author of the classic American memoir Two Years Before the Mast. Both as a writer and as a lawyer, he was a champion of the downtrodden, from seamen to fugitive slaves and freedmen.