Augusta Ada King, Countess of Lovelace (December 10, 1815 – November 27, 1852) is mainly known for having written a description of Charles Babbage's early mechanical general-purpose computer, the analytical engine.

Ada was the only legitimate child of the poet Lord Byron and his wife, Annabella Milbanke. She was named after Byron's half-sister, Augusta Leigh, by whom he was rumoured to have fathered a child. It was Augusta who encouraged Byron to marry to avoid scandal, and he reluctantly chose Annabella. On January 16, 1816, Annabella left Byron, taking 1-month old Ada with her. On April 21, Byron signed the Deed of Separation and left England for good a few days later. He was never allowed to see either again.

Ada lived with her mother, as is apparent in her father's correspondence concerning her. Lady Byron was also highly interested in mathematics (Lord Byron once called her "the princess of parallelograms"), which dominated her life, even after marriage. Her obsession with rooting out any of the insanity of which she accused Lord Byron was one of the reasons why Annabella taught Ada mathematics at an early age. Ada was privately schooled in mathematics and science, one of her tutors being Augustus De Morgan. An active member of London society, she was a member of the Bluestockings in her youth.

During a nine-month period in 1842-1843, Ada translated Italian mathematician Luigi Menabrea's memoir on Babbage's newest proposed machine, the Analytical Engine. With the article, she appended a set of Notes which specified in complete detail a method for calculating Bernoulli numbers with the Engine, recognized by historians as the world's first computer program. Biographers note, however, that the programs were written by Babbage himself, and Lovelace simply found a mistake in the first program and sent it back for amendment. The evidence and correspondence between Lovelace and Babbage indicate that he wrote all of the programs in the notes appended to the Menebrea translation. Her prose acknowledged some possibilities of the machine which Babbage never published, such as speculating that "the Engine might compose elaborate and scientific pieces of music of any degree of complexity or extent."

Ada Lovelace was bled to death at the age of 36 by her physicians, who were trying to treat her uterine cancer. Thus, she perished, ironically, at the same age as her father, and from the same cause - medicinal bloodletting. She left two sons and a daughter, Lady Anne Blunt, famous in her own right as a traveller in the Middle East and a breeder of Arabian horses.

At her request, Lovelace was buried next to the father she never knew at the Church of St. Mary Magdalene in Hucknall, Nottingham.

Her image can be seen on the Microsoft product authenticity hologram stickers.