The central theme of John Keats's 'Ode to a Nightingale' is best described as

Keats uses the nightingale's eternal song as a symbol of artistic immortality, contrasting it with human suffering, aging, and death. The poet longs to escape the 'weariness, the fever, and the fret' of mortal existence into the bird's timeless world. This tension between permanence and transience is the poem's dominant preoccupation.