What Katy Did is a children's book written by Susan Coolidge, the pen name of Sarah Chauncey Woolsey, which was published in 1872. It follows the adventures of a twelve-year-old American girl, Katy Carr, and her family who live in the fictional lakeside Ohio town of Burnet in the 1860s. Katy is a tall untidy tomboy, forever getting into scrapes but wishing to be beautiful and beloved. When a terrible accident makes her an invalid, her illness and four-year recovery gradually teach her to be as good and kind as she has always wanted.