Søren Aabye Kierkegaard (1813-1855) was a Danish philosopher, theologian, poet, and social critic. He is widely considered the first existentialist philosopher. Kierkegaard's work focused on themes such as faith, existence, and the individual's relationship with God, emphasizing personal choice and commitment. He was born on May 5, 1813, in Copenhagen, Denmark. Kierkegaard studied at the University of Copenhagen, where he initially pursued theology but later turned his attention to philosophy and literature. His writings often critiqued the established church and the philosophical systems of his time, particularly those of Hegel. He used pseudonyms to present different perspectives in his works, which include "Either/Or," "Fear and Trembling," and "The Sickness Unto Death". Despite his significant influence, Kierkegaard led a relatively solitary life, marked by his broken engagement to Regine Olsen and his ongoing struggle with melancholy. He died on November 11, 1855, in Copenhagen. Kierkegaard's ideas have had a lasting impact on existentialism, theology, and modern philosophy.