The well-known necropolis of Saqqara, 30 km (20 miles) south of Cairo, served the nearby city of Memphis and was scoured in ancient times by thieves.
The 5th Dynasty is generally understood to have lasted from 2465 to 2323 BC, while the 6th Dynasty ran from 2323 to 2150 BC. The Old Kingdom collapsed soon after, amid famine and social upheaval and a breakdown in centralized power.
Philippe Collombert, who headed the French mission that excavated Behenu's remains, said the team found her sarcophagus within the sprawling necropolis of Pepi I at Saqqara.
"It is a well-preserved granite sarcophagus engraved with the queen's different titles, but says nothing about the identity of her husband," Collombert said.
Archaeologists are unsure whether Behenu was the wife of Pepi I or Pepi II, both 6th Dynasty rulers.
Behenu's 25-meter-long pyramid was discovered in 2007 along with seven queen pyramids belonging to Inenek, Nubunet, Meretites II, Ankhespepy III, Miha, and an unidentified queen.
French mission head Philippe Collombert said the mummy of Queen Behenu was destroyed, but the chamber contained green hieroglyphics picked out on white stone known as the "Pyramid Texts."
"We are excited because the texts are well conserved," he told The Associated Press, adding that the queen's titles were written on the walls of the 33 by 16 foot (10 meter by 5 meter) burial chamber inside her small pyramid.
The text is primarily concerned with protecting the queen's remains and her transition to afterlife.
Collombert called the queen "mysterious," and said it was not clear whether she was the wife of King Pepi I or II, two long-ruling pharaohs of the Sixth Dynasty.
The 4,200-year-old burial chamber of Queen Behenu has been discovered in Saqqara in Giza.
French archaeologists digging in the necropolis of Pepi I discovered the tomb with an intact sarcophagus and a set of Pyramid Texts belonging to the queen, who had likely been a second wife of 6th dynasty Pharaoh Pepi II.
"This necropolis was quite an important place; a sacred place, even after the time of Pepi I," said Philippe Collombert, who leads the mission sponsored by the French Ministry of Foreign Affairs. "He was an important king, so probably queens from later times wanted to be buried in the same place."
Archaeologists are not 100-percent certain that the queen was in fact the wife of Pepi II, as her tomb contains no specific references to her husband. Collombert, who is also a professor at the University of Geneva, said it was uncommon during Pepi I's time to find Pyramid Texts in the tombs of queens.