The one metre (three feet) long gypsum sarcophagus portrays a woman dressed in Roman robes and contains a mummified woman or girl who died in the Greco-Roman period about 2300 years ago.
“We are sure (the mummy) is female. Either she was a small woman, and mummies always shrink, or she could have been a young woman,” Zahi Hawass, chief of the Supreme Council of Antiquities, told AFP.
The archaeologists also found a sheet of gold depicting the four sons of Horus, the ancient Egyptian sky god, and clay and glass vessels at the site in the Bahariya Oasis, some 300 kilometres (186 miles) south west of Cairo.
The site, which contained 14 graves, was first discovered during excavation work to build a youth centre, but the statement said it would be placed under the jurisdiction of the Supreme Council of Antiquities.