Merneith was a Queen in Egypt around 3000 BC in the first dynasty. There are many accepted spellings of her name such as Merytneith, MeritNit and Meryt-Neith since it is being interpreted from the original hieroglyphics. Her name means "Beloved by Neith" and Neith was a goddess with a large following in Egypt because she was a war deity whose blessing applied to the weapons of both soldiers and hunters.
Their family ruled a newly unified Egypt for a several generations. King Djer was the third pharoah of the first dynasty who ruled for about 40 years after his father Hor-Aha ruled for 62 years and his grandfather Narmer, also known as Menes, also ruled about 60 years. King Djer had a son Djet who succeeded him and ruled for 23 years. Merneith was the sister of Djet and was also his Queen. When Djet died his son Den was too young to rule and Merneith ruled until he came of age.
There is some debate whether Merneith merely ruled as a Regent or had the status of Pharoah. One point that shows she was a Pharoah was her inclusion on the Palermo Stone which recorded the kings of Egypt from the First Dynasty to the Fifth Dynasty. The way she was honored in death gives indication she was an influential ruler and buried with the status of a king. First she had two tombs with one at Abydos and another at Sakkara or Saqqara. While it was common for the kings to have two tombs no other female ruler had two tombs.
Her tomb at Abydos was in the vicinity of those of Djet and Den and was comparable in size to both. Surrounding the burial chamber were eight store rooms and over 40 smaller tombs which contained many of those that had been in her service. The tomb at Sakkara contained a solar boat which would have enabled her to travel in the afterlife with the sun god Ra. That was something that had been reserved for kings. There were also additional smaller tombs at the second tomb that contained craftsmen that were to assist her in the afterlife.
The accomplishments of her reign are unknown because little is known of the period. Egypt was still in transition after her great-grandfather Namer had unified the kingdoms of upper and lower Egypt. During the first dynasty hieroglyphics were also introduced.
One point of contention would be the actual length of the reigns. When the average life expectancy age in ancient Egypt was at 35 even for the wealthy males it seems unlikely there were reigns of 40 to 62 years. Their calendars were the same at that time. There is most likely an misinterpretation and some other measurement or milestone other than years was used. If the years are accurate then it raises the question of how they were able to live for so long.
Ancient Egypt page