Frank T. Siebert

Frank T. Siebert Jr. (1912 – 1998) was a medical doctor who became a leading authority on Algonquian languages, including Penobscot, for which he published a dictionary.

Siebert start as a medical pathologist before leaving medicine to focus on linguistics. He studied medicine at the University of Pennsylvania where apart from his medical studies he was influenced by anthropologist Frank Speck in his interest in Native American languages. He was also influenced by Franz Boas and Edward Sapir. In 1969, he became a Guggenheim fellow.

In 1980, he received a grant from the National Endowment for the Humanities for the creation of a Penobscot dictionary.

Ives Goddard of the Smithsonian Institution called Siebert "clearly the most brilliant and most competent avocational linguist working on Native American languages that there has ever been, hands down."

Siebert bequeathed his papers to the American Philosophical Society.

Siebert was born in Louisville and grew in the suburban Philadelphia. He was described as an eccentric and recluse.