Depending on the identification of the almost legendary king Menes, who is credited for the unification of Upper and Lower Egypt, Horus Aha is either considered the first or the second king of the 1st Dynasty.
As Narmer's successor, it is assumed that Aha was also Narmer's son. Several sources show his name along with that of queen Neithhotep, suggesting that she played an important role. The fact that Neithhotep was buried in a lavish tomb in the Upper Egyptian city of Naqada during the reign of Aha, has led to the assumption that Neithhotep was Aha's mother. If that is indeed the case, then her prominence in several sources may indicated that she acted as regent during Aha's early years, or that she acted as queen when Aha was not yet married. Both interpretations suggest that Horus Aha may have been quite young when he ascended the throne.
A name that has been found on several artefacts, including an ivory box found at Abydos and now on display in the Boston Museum of Fine Arts, in combination with Aha's is Benerib. The same name also occurs in a tomb located next to Horus Aha's at Umm el-Qa'ab, which, despite the absence of any title to confirm this, may suggest that Benerib was Aha's principal wife.
According to the Palermo Stone, the mother of Aha's successor, Horus Djer, was a woman named Khenthap. Thus far, no other sources naming her have been found, but if Djer was Aha's son, Khenthap may have been another wife of Aha.
Three other names -Heti, Rekhit and Saiset- have also been found in combination with Aha's name, as well as in tombs in Saqqara, Naqada and Abydos. It is obvious that these names belonged to high officials in Aha's government. The hypothesis that they were three sons of the king, is solely based on the assumption that high offices only went to members of the royal family and cannot be proven.
The Palermo Stone has recorded Aha's penultimate and last year. From the latter, we learn that Aha passed away on the 7th day of the 6th month of the calendar year. 5 more years mentioned on Cairo Fragment CF5 of the Annals Stone, may probably also be credited to him resulting in a minimum reign of 7 years.
The still rather scarce source material to have survived from Aha's reign show that the king visited several shrines throughout the country. Among them, a shrine dedicated to Nekhbet and Uto, the patron goddesses of Upper and Lower Egypt respectively, depicted on the Naqada Label. As this label has the oldest known reference to such a shrine, it is possible that it was built by Aha and it may show that if Narmer was the king to have taken control over the whole of Egypt, it was Aha who defined Egypt as the unity of Upper and Lower Egypt.
Sources also show Aha to have visited the shrine of Neith in the Lower Egyptian city of Sais and contain the oldest known representation of the Henu-bark of the Memphite god Sokar. From his reign also dates the oldest known mastaba tomb in Saqqara, part of the Memphite necropolis. This has led some to the belief that Aha was the founder of the city of Memphis, an action that tradition has credited to the almost legendary king Menes. Although this may mean that Memphis became an important centre of administration during Aha's reign, sources combining the name Ineb-Hedj, one of the names of the city, with Horus Narmer suggest that the city already existed when Aha became king.
According to one year label found in his tomb, Aha engaged in military activities against Nubia, located to the south of Elephantine.
Aha's name is also attested in Syria-Palestine, showing a continuation of the trade between Egypt and the Ancient Near East during his reign.
Aha was buried in a tomb at Umm el-Qa'ab. His burial introduces the practice of retainer sacrifice, a gruesome practice of killing and burying servants along with the king that would be maintained throughout the 1st Dynasty.