The Summer Country is the mythical birthplace of mankind in Lloyd Alexander

Lloyd Alexander

Lloyd Chudley Alexander was a widely influential American author of more than forty books, mostly fantasy novels for children and adolescents, as well as several adult books...

's fantasy book series The Chronicles of Prydain

The Chronicles of Prydain

The Chronicles of Prydain is a five-volume series of children's fantasy novels by author Lloyd Alexander...

.

The Summer Country is the ancestral home of the Sons of Don. It is ruled by the Lady Don and her consort Belin, king of the Sun. The Sons of Don had voyaged from the Summer Country to Prydain long before the story of Taran

Taran

- Given name :* Taran, a 7th century king of the Picts* Taran Taran, founder of the Taran Panth religious sect* Taran Adarsh, an Indian film critic* Taran Killam, an American comic actor* Taran Noah Smith, an actor...

. Chief Bard Taliesin

Taliesin

Taliesin was an early British poet of the post-Roman period whose work has possibly survived in a Middle Welsh manuscript, the Book of Taliesin...

 explains to the companions that it is a land without strife and suffering, even death. The Summer Country bears some similarity to the otherworlds of Atlantis

Atlantis

Atlantis is a legendary island first mentioned in Plato's dialogues Timaeus and Critias, written about 360 BC....

, Avalon

Avalon

Avalon is a legendary island featured in the Arthurian legend. It first appears in Geoffrey of Monmouth's 1136 pseudohistorical account Historia Regum Britanniae as the place where King Arthur's sword Excalibur was forged and later where Arthur was...

, Valinor

Valinor

Valinor is a fictional location in J. R. R. Tolkien's legendarium, the realm of the Valar in Aman. It was also known as the Undying Lands, along with Tol Eressëa and the outliers of Aman. This is something of a misnomer; only immortal beings were allowed to reside there, but the land itself,...

, and Tylwyth Teg

Tylwyth teg

The Tylwyth Teg is the common term in Wales for fairies. A synonym, Bendith y Mamau, means "Blessing of the Mothers". Until the early 19th century it was commonly believed that the Tylwyth Teg, described as ethereal, beautiful and fair-haired, dwelt in a number of places in Wales as genii loci...

, the kingdom of the Fair Folk. Not only is The Summer Country beautiful, but "all heart's desires are granted there...It is a land without strife or suffering, where even death itself is unknown."

In the final novel of the series, The High King

The High King

The High King is the last book in the Chronicles of Prydain fantasy series of books by Lloyd Alexander. It was awarded the Newbery Medal for excellence in American children's literature in 1969.-Plot overview:...

, Gwydion

Gwydion

Gwydion fab Dôn is a magician, hero and trickster of Welsh mythology, appearing most prominently in the Fourth Branch of the Mabinogi, which focuses largely on his relationship with his young nephew, Lleu Llaw Gyffes...

 announces that the Sons of Don must board the golden ships on which they came to Prydain and return to the Summer Country. As the age of enchantment ends in Prydain, the Sons of Don, and all others with magic in their blood, must leave its boundaries.
The Summer Country exists in the Welsh mythos

Welsh mythology

Welsh mythology, the remnants of the mythology of the pre-Christian Britons, has come down to us in much altered form in medieval Welsh manuscripts such as the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin and the Book of Taliesin....

 independently of Alexander's fiction. It is mentioned in the ancient Welsh tale Culhwch and Olwen

Culhwch and Olwen

Culhwch and Olwen is a Welsh tale about a hero connected with Arthur and his warriors that survives in only two manuscripts: a complete version in the Red Book of Hergest, ca. 1400, and a fragmented version in the White Book of Rhydderch, ca. 1325. It is the longest of the surviving Welsh prose...

as one place Arthur gathered soldiers to take to Ireland.