This paper explores Charles Darwin's scientific exploration of the Galapagos Islands and its role in the development of his theory of natural selection. The research method employed is a historical analysis of Darwin's field notes, correspondence and published works, including The Origin of Species. The results show that Darwin's observations of the unique distribution of species across the islands and the variation in their physical characteristics played a key role in his formulation of the theory of natural selection as the mechanism of evolution. The paper concludes that Darwin's work in the Galapagos Islands remains significant in contemporary evolutionary biology.