Doña Rosa (1900-1980), or Rosa Real Mateo de Nieto, was a Mexican ceramics artisan from San Bartolo Coyotepec, Oaxaca, Mexico. She is most known for creating a technique called barro negro, which made clay black and shiny after firing, in the 1950s. This created new markets for the ceramics with collectors and tourists. Although this technique made the pieces more fragile, it had made the pottery far more popular with Mexican folk art collectors, who then promoted it in the United States. The tradition of making barro negro is continued on by her daughter and grandchildren who demonstrate the technique for tourists.