Soren Aabye Kierkegaard was a Danish philosopher, theologian, and writer who is considered one of the most influential figures in existentialist philosophy. He is known for his exploration of the individual's relationship with God, the nature of faith, and the concept of subjective truth. Kierkegaard's works often delve into the complexities of human existence and the struggle to find meaning and purpose in life. His writings have had a profound impact on the fields of philosophy, theology, and literature.