Peniarth 109 is a Welsh manuscript dating to the second half of the 15th century (c. 1425 – c. 1490) in the hand of the poet Lewis Glyn Cothi.
It is part of the Peniarth Manuscripts collection at the National Library of Wales.
It is an autograph by Lewis Glyn Cothi, among the greatest of the Poets of the Nobility (Beirdd yr Uchelwyr), which contains 106 poems.
The manuscript is decorated with many illustrations, some in colour, of a noble family crests Welsh, a fact that is testament to the poet's interest in heraldry and genealogy.
The latest datable poems belong to the late 1470s, and it is fair to conclude that the manuscript was completed around this date.