"We completed the restoration ... of the first and oldest pyramid in Egypt, that of King Djoser, the founder of the Old Kingdom," Antiquities and Tourism Minister Khaled el-Enany said on Thursday at the site.
It is "the first building in the world made entirely of stone", Enany added.
The Old Kingdom is known as the age of pyramid builders. Dating to 2,680 BC, the Djoser pyramid was built under the direction of architect Imhotep.
A 1992 earthquake caused considerable damage to the monument's interior.
Renovations started in 2006 but were interrupted in 2011 and 2012 for "security reasons", before resuming in 2013, said Ayman Gamal Eddine, project manager at the antiquities ministry.
A popular uprising in Egypt in 2011 toppled longtime dictator Hosni Mubarak, with tourism one of the sectors that took a hit in the turmoil that followed.
Thursday's reopening was attended by Egyptian Prime Minister Mostafa Madbouli as well as foreign ambassadors. The premier said the renovation cost more than 104 million Egyptian pounds ($6.66 million). "We are working hard to build a new Egypt ... and the restoration of our heritage is at the top of our priorities", Madbouli said.
The gigantic Grand Egyptian Museum, overlooking the Giza pyramids, is set to open at the end of this year, five years later than originally planned.