Freedom is a necessary prerequisite for living, as most existentialists emphasized. A prominent existentialist, Sartre, fully appreciated the importance of freedom in helping humans lead authentic lives. In his philosophical magnum opus, Being and Nothingness, he boldly contends that human beings possess absolute freedom, meaning they are not determined by external factors or pre-existing essence, and are therefore responsible for creating their 'own' meaning and purpose in life. Admittedly, Sartre claims that man's freedom is tied to responsibility. He proposed the notion of freedom and responsibility as a moral compass for leading an authentic existence. This critical analysis explores Sartre's notion of existential freedom, focusing on its philosophical conceptions, implications, and deficiencies. This paper will properly understand Jean-Paul Sartre's notion of freedom and responsibility, starting by defining freedom in the way Sartre wants us to conceive it. This paper will examine some of the objections raised by Alvin Plantinga against Sartre's philosophy of freedom. And finally, this paper will also analyze Sartre's notion of freedom and responsibility and reveal its incompatibilities with universal morality. By critically evaluating Sartre's concept of existential freedom, this analysis aims to contribute to a deeper understanding of his existentialist philosophy and stimulate further dialogue on the nature and implications of human freedom.