María Rosalía Rita de Castro (Galician pronunciation: [rosaˈli.ɐ ðɪ ˈkastɾʊ]; 23 February 1837 – 15 July 1885), was a Galician poet and novelist, considered one of the most important figures of the 19th-century Spanish literature and modern lyricism. Widely regarded as the greatest Galician cultural icon, she was a leading figure in the emergence of the literary Galician language. Through her work, she projected multiple emotions, including the yearning for the celebration of Galician identity and culture, and female empowerment. She is credited with challenging the traditional female writer archetype.

Writing in Galician and Spanish, after the period known as the Séculos Escuros (lit. Dark Centuries), she became an important figure of the Galician Romantic movement, known today as the Rexurdimento ("Renaissance"), along with Manuel Curros Enríquez and Eduardo Pondal. Her poetry is marked by saudade, an almost ineffable combination of nostalgia, longing and melancholy.

She married Manuel Murguía, a member of the important literary group known as the Royal Galician Academy, historian, journalist and editor of Rosalía's books. The couple had seven children: Alexandra (1859–1937), Aura (1868–1942), twins Gala (1871–1964) and Ovidio (1871–1900), Amara (1873–1921), Adriano (1875–1876) and Valentina (stillborn, 1877). Only two of Rosalía's children married, Aura in 1897 and Gala in 1922; neither they nor their siblings left any children, and thus, today there are no living descendants of Rosalía de Castro and her husband. Their son Ovidio was a promising painter, his career cut short by early death.

Rosalía published her first collection of poetry in Galician, Cantares gallegos [gl] ("Galician Songs"), on 17 May 1863. This date, 17 May, is now known as the Día das Letras Galegas ("Galician Literature Day"), and commemorates Rosalía's achievement by dedicating, every year, this special day to a different writer, who must also write in the Galician language, since 1963. Día das Letras Galegas is an official holiday in the Autonomous Community of Galicia.

Relative poverty and sadness marked Rosalía's life, in spite of this, she had a strong sense of commitment to the poor and to the defenseless. She was a strong opponent of abuse of authority and an ardent defender of women's rights. Rosalía suffered from uterine cancer and died in Padrón, province of A Coruña, Spain, on 15 July 1885.

She is buried in the Panteón de Galegos Ilustres, a pantheon (mausoleum) in the Convent of San Domingos de Bonaval in Santiago de Compostela, Spain.

Rosalía de Castro is today one of the unquestionable poet laureates of Galicia. Highly educated, expected to speak and write in Spanish and Galician she took the bold, unconventional step of writing her early poems in the Galician language. Her defiance earned her the contempt and spite of many that deemed Galician as a Spanish dialect fit "only for the illiterate and the churlish". However, Rosalía's defiant gesture won her the love and admiration of the common folk, who spoke Galician at home or on a daily basis.

Schools in Galicia, in Spain, in Russia and in Uruguay, libraries, cultural associations, awards, parks, folklore groups, choirs, compositions of her poems, a Galician traditional morning song adorned with the lyrics of one of her poems, a professional sports team, monuments at home and abroad, a theater, restaurants, a label of white wine, lodgings, a banknote formerly in circulation, a postage stamp, a FS98 Iberia Airbus A340, a sea-rescue plane, a school train and many streets have all taken her name.