Literary criticism is the study, discussion, evaluation, and interpretation of literature. Modern literary criticism is often informed by literary theory, which is the philosophical discussion of its methods and goals. Though the two activities are closely related, literary critics are not always, and have not always been, theorists.

Whether or not literary criticism should be considered a separate field of inquiry from literary theory, or conversely from book reviewing, is a matter of some controversy. For example, the Johns Hopkins Guide to Literary Theory and Criticism draws no distinction between literary theory and literary criticism, and almost always uses them together to describe the same concept. Some critics consider literary criticism a practical application of literary theory, because criticism always deals directly with a literary work, albeit from a theoretical point of view.

Modern literary criticism is often published in essay or book form. Academic literary critics teach in literature departments and publish in academic journals, and more popular critics publish their criticism in broadly circulating periodicals such as the Times Literary Supplement, the New York Times Book Review, the New York Review of Books, the London Review of Books, The Nation, and The New Yorker.

Classical and medieval criticism

Literary criticism has probably existed for as long as literature. Aristotle wrote the Poetics, a typology and description of literary forms with many specific criticisms of contemporary works of art, in the 4th century BC. Poetics developed for the first time the concepts of mimesis and catharsis, which are still crucial in literary study. Plato's attacks on poetry as imitative, secondary, and false were formative as well. Around the same time, Bharata Muni, in his Natya Shastra, had written literary criticism on ancient Indian literature and Sanskrit drama.

Later classical and medieval criticism often focused on religious texts, and the several long religious traditions of hermeneutics and textual exegesis have had a profound influence on the study of secular texts. This was particularly the case for the literary traditions of the three Abrahamic religions: Jewish literature, Christian literature and Islamic literature.

Literary criticism was also employed in other forms of medieval Arabic literature and Arabic poetry from the 9th century, notably by Al-Jahiz in his al-Bayan wa-'l-tabyin and al-Hayawan, and by Abdullah ibn al-Mu'tazz in his Kitab al-Badi.

Renaissance criticism

The literary criticism of the Renaissance developed classical ideas of unity of form and content into literary neoclassicism, proclaiming literature as central to culture, entrusting the poet and the author with preservation of a long literary tradition. The birth of Renaissance criticism was in 1498, with the recovery of classic texts, most notably, Giorgio Valla's Latin translation of Aristotle's Poetics. The work of Aristotle, especially Poetics, was the most important influence upon literary criticism until the latter eighteenth century. Lodovico Castelvetro was one of the most influential Renaissance critics who wrote commentaries on Aristotle's Poetics in 1570.