Within his poetic imagination, John Milton frames the relationship between God and humanity around two cardinal doctrines: humanity’s prelapsarian state of harmony with God and humanity’s separation from God through original sin. Milton relies upon figurative language and images to articulate this binary of harmony and separation, or concord and discord. Although scholarship has devoted significant attention to images of harmony and discord in Milton’s poetry, very little attention has been given uniquely to discord, and even less to Milton’s many usages of the word in theological, interpersonal, allegorical, and musical or auditory contexts. Arguing for the significance of discord within Milton’s poetic imagination, this thesis traces the persistent presence of discord across Milton’s poetry; characterizes his understanding of discord with respect to its polysemy; and emphasizes that, despite relying upon varied usages, Milton insistently associates discord with original sin.