Pengolodh (also spelled Pengolod Pengoloð, Pengoloth, and Pengoloþ — the ending in all cases representing the voiced dental fricative) was a Loremaster of the Noldor. He appears only in the The History of Middle-earth and not the 'canonical' major published works.
Pengolodh was a Noldorin Elf of Gondolin, who was born in Nevrast to a Noldorin lord and a Sindarin lady. Early tales about the Fall of Gondolin mention him as one of the lords of the city, and ruler of the "Twin Folk of the Pillar and the Tower of Snow". As a member of the Lambengolmor, he was known as the Sage of the Noldor, and counted as the greatest Loremaster since Fëanor and Rúmil. He was also the tallest of the Elves of Gondolin.
Pengolodh escaped the sack of the city with Tuor and Idril, and followed them to the Havens of Sirion. He is not further mentioned in writing, but since the Annals of Beleriand are attributed to him, as well as the edited Annals of Aman (furthering the work of Rúmil), he must have stayed in Lindon for at least a while after the War of Wrath, so that the Dúnedain could copy his work.
It was during his stay at the Mouths that Pengolodh did the majority of his work. Basing on information obtained from the refugees of Doriath, he made copies and extracts of documents written in Cirth, possibly preserving them as an active writing system.
Later, in the Second Age, he dwelt in the Kingdom of Ereinion Gil-galad. Pengolodh was one of the few Elves admitted into Khazad-dûm, where he might have learned Khuzdul. Pengolodh left Middle-earth during the War of the Elves and Sauron and after the fall of Eregion, and left for Tol Eressëa, last of the Loremasters to leave Middle-earth.
Pengolodh does not appear in any of the canon works of Middle-earth, but in The History of Middle-earth he is given as the author of many works, including the Annals of Beleriand, a work which was developed by Tolkien at the same time as The Silmarillion, and from which Christopher Tolkien drew much information to establish the published Silmarillion. Various late essays by Tolkien dealing with linguistics are presented as being the work of Pengolodh, including the remarkable work Quendi and Eldar.
Early Tolkien texts stated that, after removing to Tol Eressëa, Pengolodh dwelt in a village called Tavrobel (or Tathrobel). Centuries later Ælfwine spoke with him there. The figure of Gilfanon, which fulfilled a similar role as a chronicler of the annals of Beleriand in earlier works, probably became this character as well in Tolkien's mind.