Lake Nasser is a vast reservoir in southern Egypt and northern Sudan. It is one of the largest man-made lakes in the world. Before construction, Sudan was against the building of Lake Nasser because it would encroach on land in the North, where the Nubian people lived. They would have to be resettled. In the end Sudan's land near the area of Lake Nasser was mostly flooded by the lake.
Strictly, "Lake Nasser" refers only to the much larger portion of the lake that is in Egyptian territory, with the Sudanese preferring to call their smaller body of water Lake Nubia.