Charles Darwin first used the phrase “survival of the fittest” in On the Origin of Species in 1869.
The phrase appeared in the fifth edition of the book, published in 1869. Darwin added it as a companion expression to “natural selection,” including it in the heading of the chapter explaining how favorable variations are preserved. Earlier editions, beginning with the first edition of 1859, did not contain the phrase.
Darwin did not coin the wording. Philosopher Herbert Spencer introduced “survival of the fittest” in his Principles of Biology in 1864, after reading Darwin’s original work. Darwin later adopted Spencer’s phrase because he considered it a useful shorthand for natural selection.
The expression is often misunderstood as meaning that the strongest individuals always survive. In evolutionary biology, “fittest” means best suited to a particular environment, including traits that improve reproduction. Darwin continued using “natural selection” as the central scientific term, while treating Spencer’s phrase as an explanatory synonym.