"Gerontion" is a poem by T. S. Eliot (26 September 1888 – 4 January 1965), an American poet who became a British citizen in 1937. It was first published in 1920 and originally written as a response to World War I.

The poem is written in stanzas of irregular length. The meter of the poem is free verse, i.e. it has no consistent rhythmical pattern nor does it have regular rhymes, although it employs many poetic devices including assonance and alliteration.

The narrator of the poem is an old man. The poem, which Eliot had at one point considered publishing as a preface to "The Wasteland," is a dramatic monologue reflecting on the decay and fragmentation of modern life, especially in terms of its secular and rootless nature.

The poem takes as an epigraph lines from Act III of Shakespeare's play Measure for Measure, from a speech that is an extended meditation on old age and death. The narrator of Eliot's poem is himself close to death and reflects on his own mortality in terms of the decay of civilization. As in "The Wasteland," Eliot uses imagery of dryness and withering to link the image of the aging fisher king to the decline of the fertility of the kingdom and land. The old man is waiting among the ruins of his own life and western civilization, hoping for a sign of renewal, which is identified with rain.

Christ appears as an ambivalent figure, who may be part of both the old world that is fading and the world that might be reborn. Christ is part of the youth of the world, but the present of the poem is one of old age; the second coming of Christ is a distant and uncertain possibility in the poem, that might bring destruction or renewal, the narrator, though, has lost faith, hope, and the strength needed for renewal:

I have lost my passion: why should I need to keep it
Since what is kept must be adulterated?
I have lost my sight, smell, hearing, taste and touch . . .

Instead, any potential hope for the future must rest in a new generation that can somehow transform or thrive in the fragmented post-apocalyptic modern world. The old man who narrates the poem, though, cannot see forward to the future but only sees the fragments of the past and the deceptions and melancholy lessons of history.