Baroness Emma Magdalena Rozália Mária Jozefa Borbála Orczy de Orci (/ˈɔːrtsiː/; 23 September 1865 – 12 November 1947), usually known as Baroness Orczy (the name under which she was published), was a Hungarian-born British novelist and playwright. She is best known for her series of novels featuring The Scarlet Pimpernel, the alter ego of Sir Percy Blakeney, a wealthy English fop who turns into a quick-thinking escape artist in order to save French aristocrats from "Madame Guillotine" during the French Revolution, establishing the "hero with a secret identity" in popular culture.

Opening in London's West End on 5 January 1905, The Scarlet Pimpernel became a favourite of British audiences. Some of Orczy's paintings were exhibited at the Royal Academy in London. She established the Women of England's Active Service League during World War I with the intention of empowering women to convince men to enlist in the military.

Orczy was born in Tarnaörs, Hungary. She was the daughter of the composer Baron Félix Orczy de Orci (1835–1892) and Countess Emma Wass de Szentegyed et Cege (1839–1892). Her paternal grandfather, Baron László Orczy (1787–1880), was a royal councillor, and knight of the Sacred Military Constantinian Order of Saint George; her paternal grandmother, Baroness Magdolna, born Magdolna Müller (1811–1879), was of Austrian origin. Her maternal grandparents were the Count Sámuel Wass de Szentegyed et Cege (1815–1879), member of the Hungarian parliament, and Rozália Eperjessy de Károlyfejérvár (1814–1884).

Orczy's parents left their estate for Budapest in 1868, fearful of the threat of a peasant revolution. They lived in Budapest, Brussels, and Paris, where she studied music unsuccessfully. In 1880, at age 14, Emma and her family moved to London, England where they lodged with their Francis Pichler at 162 Great Portland Street. Orczy attended West London School of Art and then the Heatherley School of Fine Art.^{[citation needed]}

At art school she met illustrator Henry George Montagu MacLean Barstow, the son of an English clergyman; they were married at St Marylebone parish church on 7 November 1894. It was the start of what she described as a joyful and happy marriage, "for close on half a century, one of perfect happiness and understanding, of perfect friendship and communion of thought."

They had very little money and Orczy started to work with her husband as a translator and an illustrator to supplement his meager earnings. John Montague Orczy-Barstow, their only child, was born on 25 February 1899 (died 1969). She started writing soon after his birth, but her first novel, The Emperor's Candlesticks (1899), was a failure. She did, however, find a small following with a series of detective stories in the Royal Magazine. Her next novel, In Mary's Reign (1901), did better.

In 1903, she and her husband wrote The Scarlet Pimpernel, a play based on one of her short stories about an English aristocrat, Sir Percy Blakeney, Bart., who rescued French aristocrats from the French Revolution. She had conceived the character while standing on a platform on the London Underground. She submitted her novelisation of the story under the same title to 12 publishers. While the couple waited for the decisions of these publishers, Fred Terry and Julia Neilson accepted the play for production in London's West End. Initially, it drew small audiences, but the play ran for four years in London, and broke many stage records, eventually playing more than 2,000 performances and becoming one of the most popular shows staged in Britain. It was translated and produced in other countries and underwent several revivals. This theatrical success generated huge sales for the novel. The couple moved to Thanet, Kent.

Introducing the notion of a "hero with a secret identity" into popular culture, the Scarlet Pimpernel exhibits characteristics that would become superhero conventions, including the penchant for disguise, use of a signature weapon (sword), ability to out-think and outwit his adversaries, and a calling card (he leaves behind a scarlet pimpernel at each of his interventions). By drawing attention to his alter ego, Blakeney hides behind his public face as a slow-thinking, foppish playboy, and he also establishes a network of supporters, The League of the Scarlet Pimpernel, who aid his endeavours.