Themistoclea was a priestess, philosopher and mathematician

Mathematician

A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

 at Delphi

Delphi

Delphi is both an archaeological site and a modern town in Greece on the south-western spur of Mount Parnassus in the valley of Phocis.In Greek mythology, Delphi was the site of the Delphic oracle, the most important oracle in the classical Greek world, and a major site for the worship of the god...

.. According to surviving sources she was Pythagoras

Pythagoras

Pythagoras of Samos was an Ionian Greek philosopher, mathematician, and founder of the religious movement called Pythagoreanism. Most of the information about Pythagoras was written down centuries after he lived, so very little reliable information is known about him...

’ teacher, although she may also have been his sister. After Pythagoras coined the term "philosophy", she became the first woman in history to whom the word "philosopher" was applied.

Themistoclea is mentioned in the writings of Aristoxenus

Aristoxenus

Aristoxenus of Tarentum was a Greek Peripatetic philosopher, and a pupil of Aristotle. Most of his writings, which dealt with philosophy, ethics and music, have been lost, but one musical treatise, Elements of Harmony, survives incomplete, as well as some fragments concerning rhythm and...

 and Diogenes Laertius

Diogenes Laertius

Diogenes Laertius was a biographer of the Greek philosophers. Nothing is known about his life, but his surviving Lives and Opinions of Eminent Philosophers is one of the principal surviving sources for the history of Greek philosophy.-Life:Nothing is definitively known about his life...

. In his biography of Pythagoras in Lives and Opinions of Eminent Philosophers

Lives and Opinions of Eminent Philosophers

Lives and Opinions of Eminent Philosophers is a biography of the Greek philosophers by Diogenes Laërtius, written in Greek, perhaps in the first half of the third century AD.-Overview:...

, Diogenes cites Aristoxenus’ statement that she taught Pythagoras his moral

Moral

A moral is a message conveyed or a lesson to be learned from a story or event. The moral may be left to the hearer, reader or viewer to determine for themselves, or may be explicitly encapsulated in a maxim...

 doctrines: “Aristoxenus asserts that Pythagoras derived the greater part of his ethical

Ethics

Ethics, also known as moral philosophy, is a branch of philosophy that addresses questions about morality—that is, concepts such as good and evil, right and wrong, virtue and vice, justice and crime, etc.Major branches of ethics include:...

doctrines from Themistoclea, the priestess at Delphi.”