Dada Masilo, a South African dancer and choreographer known for injecting African dance into bold, unconventional interpretations of classical ballets like “Swan Lake” and “Giselle,” died on Sunday in Johannesburg. She was 39. The death, in a hospital, was confirmed by Bridget van Oerle, a spokeswoman for Ms. Masilo’s family, who said she died unexpectedly after a brief illness. Ms. Masilo built a reputation as a fearless choreographer who deconstructed long-performed ballet classics and fused them with African dance styles. Her interpretations of classic stories — including “Romeo and Juliet,” “Carmen” and “Hamlet” — intrigued critics and won the admiration of audiences in South Africa and abroad. “In the beginning, I battled just to make them speak to each other,” Ms. Masilo said in a 2014 interview, of fusing African dance moves with ballet. “I thought, OK, let me just try.” Among her most lauded works was a gay spin on the 19th century ballet “Swan Lake” in which Odette, played by Ms. Masilo, is married off to Prince Siegfried, who pines after a male Odile. Ms. Masilo said she wanted her “Swan Lake” to break gender stereotypes.