"O Captain ! My Captain !" is a poem written by Walt Whitman(1819-1892) in 1865. The poem is classified as an elegy or mourning poem, and was written to honor Abraham Lincoln, the 16th president of the United States.

 O Captain ! My Captain ! our fearful trip is done ;
 The ship has weather’d every rack, the prize we sought is won ;
 The port is near, the bells I hear, the people all exulting,
 While follow eyes the steady keel, the vessel grim and daring :

 But O heart ! heart ! heart !
 O the bleeding drops of red,
 Where on the deck my Captain lies,
 Fallen cold and dead.

 O Captain ! My Captain ! rise up and hear the bells ;
 Rise up—for you the flag is flung—for you the bugle trills ;
 For you bouquets and ribbon’d wreaths—for you the shores a-crowding ;
 For you they call, the swaying mass, their eager faces turning ;

 Here captain ! dear father !
 This arm beneath your head ;
 It is some dream that on the deck,
 You’ve fallen cold and dead.

 My Captain does not answer, his lips are pale and still ;
 My father does not feel my arm, he has no pulse nor will ;
 The ship is anchor’d safe and sound, its voyage closed and done ;
 From fearful trip, the victor ship, comes in with object won ;

 Exult, O shores, and ring, O bells !
 But I, with mournful tread,
 Walk the deck my captain lies,
 Fallen cold and dead.

You can read a translation here.

Here is another one from "leaves of grass"

Walt Whitman (1819–1892). Leaves of Grass. 1900.

166. O Me ! O Life !

 O ME ! O life !... of the questions of these recurring ;
 Of the endless trains of the faithless—of cities fill’d with the foolish ;
 Of myself forever reproaching myself, (for who more foolish than I, and who more faithless ?)
 Of eyes that vainly crave the light—of the objects mean—of the struggle ever renew’d ;
 Of the poor results of all—of the plodding and sordid crowds I see around me ;
 Of the empty and useless years of the rest—with the rest me intertwined ;
 The question, O me ! so sad, recurring—What good amid these, O me, O life ?

Answer.

 That you are here—that life exists, and identity ;
 That the powerful play goes on, and you will contribute a verse.

You can find a translation here.