CANTREF BYCHAN The Little Cantref.
- Inland district in southern Wales, the northeast of a region called Ystrad Tywi, the Towy valley;
- A Marcher lordship, smaller in extent.
Cantref Bychan lay on the left bank (generally the east bank) of the Tywi, and belonged to the Welsh Kingdoms of Seisyllwg (10th century) and Deheubarth (11th century). Early in the 12th century Normans penetrated Cantref Bychan and the ancestor of the family of Clifford built a castle at Llandovery, but the revived Kingdom of Deheubarth drove them out in 1136 and except for the years 1158-62 Cantref Bychan remained in Welsh hands until 1282.
It then became two Marcher lordships, that of Is-Cennen (the south of the old cantref) and that of Cantref Bychan, focussed on Llandovery (Llanymddyfri). These were to some degree subservient to the royal authorities at the castle of Carmarthen. In 1536 the lordship of Cantref Bychan became the northeast of the county of Carmarthenshire.