A philosopher is someone who practices philosophy. The term "philosopher" comes from the Ancient Greek, φιλόσοφος (philosophos), meaning "lover of wisdom". The coining of the term has been attributed to the Greek thinker Pythagoras (6th century BC).

In the classical sense, a philosopher was someone who lived according to a certain way of life, focusing on resolving existential questions about the human condition, and not someone who discourses upon theories or comments upon authors. Typically, these particular brands of philosophy are Hellenistic ones and those who most arduously commit themselves to this lifestyle may be considered philosophers. A philosopher is one who challenges what is thought to be common sense, doesn't know when to stop asking questions, and reexamines the old ways of thought.

In a modern sense, a philosopher is an intellectual who has contributed in one or more branches of philosophy, such as aesthetics, ethics, epistemology, logic, metaphysics, social theory, and political philosophy. A philosopher may also be one who worked in the humanities or other sciences which have since split from philosophy proper over the centuries, such as the arts, history, economics, sociology, psychology, linguistics, anthropology, theology, and politics