Endymion is a beautiful young shepherd and leader on Mount Latmos whose ambitions begin to extend beyond the earthly world. Though outwardly participating in the community's rituals, he suffers from a deep melancholy and falls into catatonic trances. His waking life becomes consumed by an overwhelming, divine vision he experiences in a poppy-induced sleep.

Peona is Endymion's devoted sister who serves as his primary caretaker. She possesses practical wisdom and favors earthly honor over chasing fleeting celestial visions. Adept at moving through the physical world, she captains a small boat called a shallop and plays soothing melodies on her lute to heal her brother's troubled mind inside a quiet island bower.

A divine celestial being whose overwhelming beauty completely captivates Endymion. She manifests in his dreams with bright blonde hair braided up to reveal her ears, wearing a blue scarf patterned with eyes that resemble daisies. Her interactions with Endymion blend the physical sensations of earthly love with the vast, ethereal nature of deep space and the ocean.

The spiritual leader of the shepherd community on Mount Latmos, recognizable by his white hair crowned with a beechen wreath. He expresses gratitude for the community's agricultural bounty and good weather. His focus on earthly harvest and ritual fire contrasts with Endymion's watery, celestial fixations.

The first-person narrator of the poem represents Keats himself. Residing in the idyllic countryside, he guides his own symbolic boat of poetic thought. He sets out to retell the ancient Latmian myth over the course of four seasons, seeking inspiration from the natural world and the enduring power of beauty.

The satyr god of nature and patron of shepherds whom the Latmos community worships. He rules over the intersection of earth and ocean, assisting farmers with problematic rams, wild boars, and the weather. The community sings a long, devoted hymn praising his immense power and his affinity for tree-dwelling mythological creatures.

Echo is a nymph residing in a secret, watery cave. She listens to Endymion's sorrowful pleas and promises to carry the sighs and sounds of his physical affection to his beloved moon goddess.