Charles Darwin was a renowned naturalist and biologist best known for his groundbreaking work on the theory of evolution. His most famous publication, On the Origin of Species, introduced the concept of natural selection, explaining how species evolve over time through the survival of the fittest. Darwin's observations during his voyage on the HMS Beagle led him to develop his ideas about the diversity of life on Earth. His work laid the foundation for modern evolutionary biology and has had a profound impact on our understanding of the natural world.