Florence Nightingale, OM, RRC (pron.: /ˈflɒrəns ˈnaɪtɨŋɡeɪl/; 12 May 1820 – 13 August 1910) was a celebrated English social reformer and statistician, and the founder of modern nursing. She came to prominence while serving as a nurse during the Crimean War, where she tended to wounded soldiers. She was dubbed "The Lady with the Lamp" after her habit of making rounds at night.

Early 21st century commentators have asserted Nightingale's achievements in the Crimean War had been exaggerated by the media at the time, to satisfy the public's need for a hero. But her later achievements remain widely accepted. In 1860, Nightingale laid the foundation of professional nursing with the establishment of her nursing school at St Thomas' Hospital in London. It was the first secular nursing school in the world, now part of King's College London. The Nightingale Pledge taken by new nurses was named in her honour, and the annual International Nurses Day is celebrated around the world on her birthday. Her social reforms include improving healthcare for all sections of British society; improving healthcare and advocating for better hunger relief in India; helping to abolish laws regulating prostitution that were overly harsh to women; and expanding the acceptable forms of female participation in the workforce. Nightingale was a prodigious and versatile writer. In her lifetime much of her published work was concerned with spreading medical knowledge. Some of her tracts were written in simple English so they could easily be understood by those with poor literary skills. She helped popularize the graphical presentation of statistical data. Much of her writing, including her extensive work on religion and mysticism, has only been published posthumously.

Nightingale was born to a wealthy upper-class family, at a time when women of her class were expected to focus on marriage and child bearing. Unitarian religious inspiration led her to devote her life to serving others, both directly and as a reformer. Nightingale rejected proposals of marriage so as to be free to pursue her calling. Her father had progressive social views, providing his daughter with a well-rounded education that included mathematics and supported her desire to lead an active life. Nightingale's ability to effect reform rested on her exceptional analytic skills, her high reputation, and her network of influential friends. Starting in her mid thirties, she suffered from chronic poor health, but continued working almost until her death at the age of ninety.