Henry IV, First Part (often written as 1 Henry IV) is a history play by William Shakespeare, believed to have been written no later than 1597. The play dramatises part of the reign of King Henry IV of England, beginning with the battle at Homildon Hill late in 1402, and ending with King Henry's victory in the Battle of Shrewsbury in mid-1403. In parallel to the political conflict between King Henry and a rebellious faction of nobles, the play depicts the escapades of King Henry's son, Prince Hal (the future King Henry V), and his eventual return to court and favour.

Henry IV, Part 1 is the first of Shakespeare's two plays which deal with the reign of Henry IV (the other being Henry IV, Part 2), and the second play in the Henriad, a modern designation for the tetralogy of plays that deal with the successive reigns of Richard II, Henry IV, and Henry V. From its first performance on, it has been an extremely popular work both with the public and critics.