A nomarch in ancient Egypt was a provincial governor, the regional authority over one of the 40 or so nomes (Egyptian: sepat) into which the country was divided.

The position of the nomarch was at times hereditary, while at others they were appointed by the pharaoh. The balance of power between nomarchs and the central government varied from one pharaoh's rule to the next. Generally, when the national government was stronger, nomarchs were appointed governors. But when the central government was weaker – at times of foreign invasion or civil war, for example – individual nomes would assert themselves and establish hereditary lines of succession. Conflicts between these different hereditary nomarchies were common during, for example, the First Intermediate Period – a time that saw a breakdown in central authority lasting from the sixth and eleventh dynasties, until one of the local rulers was able once again to assert control over the entire country as pharaoh.