Martin Heidegger (26 September 1889 – 26 May 1976) was a German philosopher best known for his contributions to phenomenology, hermeneutics, and existentialism. Often considered one of the most important and influential philosophers of the 20th century, Heidegger's work has had a profound impact on a wide range of fields, including architecture, literary criticism, theology, and cognitive science.

In 1927, Heidegger published Being and Time, introducing the term Dasein to describe the type of being that humans possess. This work initiated his exploration into the question of the meaning of being, analyzing how entities appear as the specific entities they are. Heidegger's philosophy underwent a significant shift in the 1930s, known as "the Turn," with works such as Letter on Humanism and Introduction to Metaphysics, aiming to pave a new path for his thought beyond metaphysics.

Despite his groundbreaking contributions to philosophy, Heidegger's legacy is controversial due to his involvement with the Nazi Party during his tenure as rector of the University of Freiburg and his support for Adolf Hitler. This aspect of his life has fueled ongoing debate about the relationship between his philosophy and Nazism.