The famous historical figure associated with the phrase "I think, therefore I am" is René Descartes, a French philosopher, mathematician, and scientist. This statement, originally in Latin as "Cogito, ergo sum," appears in his work "Meditations on First Philosophy," written in 1641. Descartes used this phrase to illustrate the fundamental element of knowledge and existence: the act of thinking implies a thinking self. This idea laid the groundwork for modern philosophy and emphasized rationalism's role in understanding reality, significantly influencing various fields, including science, mathematics, and epistemology.