Early Welsh poetry is epic, romantic, and historical. Songs in praise of heroes (many pre-Christian and mythological) and elegiac poems of desolation and longing frequently appear. They are marked by a rich, musical style, displaying the verbal felicity of a highly developed art. Among early prose survivals, the classic is the Mabinogion (set down c.1060). In this work the cycle of stories concerning the old Celtic gods and heroes—similar to those in Irish and Arthurian literature—is expanded by the addition of later stories and partly transformed by numerous Welsh revisions.

Early medieval prose includes The History of the Kings of Britain and romances and stories of the Holy Grail, partly adopted from French and other sources, but showing native Welsh style and story innovations. In poetry, the Gogynfeirdd (early medieval period) eulogized the heroes of the North, but it is lyrical rather than epic. From c.1150 the bardic system, with its archaisms, its prescribed themes and meters, and its aim of "exquisiteness," flowered; of the several levels of bardic verse, eulogy was considered the highest and was preserved.

The 14th cent. was a golden age in South Wales. Dafydd ap Gwilym, considered by many to be the greatest Welsh poet, broke the classical eulogistic traditions of the bards and established new horizons. Dafydd was influenced by Provençal poetry, but his verse was more informal and spontaneous. With a simpler, more personal diction and a fuller cognizance of nature than had been present in Welsh verse, he elevated love poetry over the eulogistic variety.

Dafydd influenced Welsh poetry for 200 years, inaugurating the Cywyddwyr period named after the cywydd meter (a 7-syllable rhymed couplet with alternating endings in masculine and feminine genders), which he introduced. This poetry achieved perfection in the 15th cent. and declined after the mid-16th. The bards overlaid the cywydd with an excessively formal, alliterative style, as they did with the more natural, spontaneous English poetry that began to be popular in the 16th cent.

After the 16th cent., social and political changes in Wales had marked effects, especially the anglicization of the Welsh gentry and the gradual decline of patronage for the native language. Influence from religious sources grew. Early modern Welsh prose standards were partly set by Bishop William Morgan's translation of the Bible (1583). Welsh humanist prose of the 16th and 17th cent., although not much published in the original tongue, was polished and musical.

In the 18th cent. theological and pedagogical writings dominated, but such authors as Morgan Llwyd, Theophilus Evans, and Ellis Wynn created clear, elegant prose classics. Religious feeling and the interest of the clergy were significant in keeping Welsh poetry alive during the 18th cent. The priest Goronwy Owen and other members of the "Morris School" attempted to assimilate the early, free cywydd poetry to modern situations. Meanwhile, the great Methodist hymnodists, William Williams (Pantycelyn) and Ann Griffiths, deriving elements from the abundant folk verse (penillion), created a more personal poetry in "free" meters. They were a potent influence on the 19th-century lyric poets, Ceiriog (John Ceiriog Hughes) and Islwyn.

Improved popular education, as sponsored by the Welsh-language publications of the Society for the Dissemination of Christian Knowledge, and increased Welsh political consciousness, as exemplified in the 19th cent. by the writings of Daniel Owens ("the Welsh Dickens"), gave rise to a literary revival that reached a high point in the 20th cent. In addition, the Welsh poetic revival, which produced both nationalist and cosmopolitan works, was tied to the founding in 1872 of the new Univ. of Wales.

In the 20th cent. attempts at language purification, interest in Welsh mythology, and a turning away from earlier Welsh puritanism have accompanied influences ranging from the Greek classics to modern French symbolists in the making of a Welsh literary revival. Other dominating trends are the love of nature, the boldness of imagery, and the lilt of language, best represented in the free-metered works of W. J. Gruffydd and the more classical poetry of T. Gwynn-Jones. The short story has been developed to a high level by Dewi Williams, Islwyn Williams, and Kate Roberts.

The principal novelists of the 20th cent. include Kate Roberts, Tegla Davies, T. Rowland Hughes, and Islwyn Ffowc Ellis. Realistic drama was developed by R. G. Berry, D. T. Davies, Saunders Lewis, and W. J. Gruffydd. A more symbolic and psychological dramatic literature followed with the works of Huw Lloyd Edwards, T. Parry, and Gwilym R. Jones. The poet and dramatist Saunders Lewis has enriched Welsh critical writing. The eisteddfod remains a vigorous cultural force.