The Book of Cynog (la-x-medieval|Liber Knauc; wlm|Llyfr Kynawc; cy|Llyfr Cynog) was a text of medieval Welsh law.[1] It is quoted extensively by surviving sources but does not appear to have survived intact. However, the first 75 folios of Peniarth MS. 35 seem to be a medieval attempt to reconstruct the earlier book.[2]