Sadly no, it’s not Yoda, but a great illustration from a 14th Century medieval manuscript, the Smithfield Decretals. See more medieval monsters at the British Library’s blog. (Also, that beautiful blackletter calligraphy!) From the Telegraph:
Stuart Freeman, the British make-up artist who first created the look of the character Yoda for the 1980 Star Wars’ film The Empire Strikes Back, always said he based the puppet’s face on his own, and modelled the eyes on Albert Einstein to give him a kindly but wise look. But a younger version of the fictional Jedi master, who was already 900 years old in the early films, may have been uncovered in a medieval manuscript dating from the 14th century.
British Library curator Julian Harrison spotted the likeness to the Star War’s character in the medieval manuscript known as the Smithfield Decretals. The image, posted on Harrison’s blog Medieval Manuscripts, shows a crouching green figure with large pointed ears and spiky hands, similar to the look of Yoda in George Lucas’s films.
The French manuscripts actually depict the biblical story of Samson and Harrison says it is not clear who the green figure represents. Yoda first appeared in the second film in the original Star Wars trilogy as mentor to the young Luke Skywalker.