The main theme of Walt Whitman's poem "O Captain! My Captain!" is the profound grief and mourning over the loss of a great leader, intertwined with a bittersweet celebration of victory. The poem is an extended metaphor for the assassination of President Abraham Lincoln, with the "Captain" representing Lincoln and the "ship" symbolizing the United States. The poem expresses the sorrow felt after Lincoln's death despite the successful end of the Civil War, which is depicted as a perilous voyage that the ship has weathered. The speaker moves through stages of grief-shock, denial, and acceptance-while contrasting the public's jubilant celebration with his own personal mourning. The victory is overshadowed by the tragic loss of the captain, emphasizing both national triumph and deep personal and collective sorrow

. In summary, the poem mourns the death of a heroic figure who led the nation through a difficult journey, celebrating the achievement while lamenting the cost of that victory