The County of Namur (Dutch: Namen) was a county of the Holy Roman Empire with its military and administrative capital at the town of Namur, at the merging of the Sambre and Meuse rivers in what is now French-speaking Belgium. Under this name it existed from about 990 until about 1790.

Like most of what is now Belgium, during the 15th century the County of Namur became part of the Burgundian Netherlands, which subsequently became a possession of the kings of Spain, and later of Austria. Like its neighbours, the county ceased to exist during the French Revolution, when the entire region was conquered by the revolutionary French Republic.

The modern Belgian province of Namur is larger than the old county. The boundaries of the province are based upon those of the French départment of Sambre-et-Meuse, and stretch further eastwards and southwards.

The city of Namur most likely arose around 'the Champeau', a rocky hill between the Sambre and Meuse rivers. Numerous prehistoric flint weapons have been found in the area. During Roman times, the region around Namur was first mentioned in Julius Caesar's Commentarii de Bello Gallico in the second half of the 1st century BC. The exact boundaries of the peoples he mentioned are not known, but to the west of Namur were the Nervii, and to the east the Germani cisrhenani. It has been suggested that Namur itself may have been within the territory of the Aduatuci who Caesar described as descendants of the Cimbri and Teutons, whose main main fort was possibly at Thuin.) Caesar and the Romans conquered the Belgae cities and their territory were incorporated into the Roman Empire.

From at least the 8th century, the larger region between the Sambre and Meuse rivers was in fact commonly referred to as the gau or pagus of Lomme (the pagus Lomacensis in Latin, or Lommegau in German), which also stretched north of the river junction, at least as far as Gembloux. From at least about 800, this region was one of the ones under the religious jurisdiction of the bishopric of Liège, along with Hasbania, Condroz and the Ardennes to the west of it.

During the late 9th century, and throughout the 10th century, there are also references to a county of Lomme (comitatus Lomacensis), apparently indicating that this region had only one count. In the year 832 a document by Emperor Louis the Pious indicates that at least part of the region could be referred to as the pagus of Namur, because it refers to Beez and Wépion, two places now within the city of Namur, as being in the countryside (pagus) of Namur (Latin: in pago Namurcensis). There was however no mention is this period of any county or count of Namur. During the 10th century, records mentioning local counts Berengar, his possible descendant Robert, and Robert's son Albert I, demonstrate that the counts of Lomme were established at a fort in Namur. Berengar was referred to as a count of Namur in 919, but it is only in the time of Albert that the normal terminology changed. An imperial document of 992 calls Albert a count of Namur. Another imperial document of 986 refers to a county of Namur, when it says that Brogne was in the pagus of Lomme, and the county of Namur. After this period, the term Lomme was no longer used.

Albert III (1063–1102) took over some positions which had been held by his wife's previous husband, including the office of advocate of the Princely Abbey of Stavelot-Malmedy. Until the start of the 12th century, Namur was threatened by its powerful neighbours Brabant, Hainaut and Liège. Important parts of the county were annexed. The city of Dinant, for example, came into possession of Liège. From the 12th century on, the counts of Namur managed to more or less compensate for the losses they had suffered. Count Godfrey, for example, acquired the county of Longwy, thanks to his marriage with Ermesinde of Luxembourg.

The last ruler in the first line that ruled Namur was Henry the Blind (1139–96), who also inherited the counties of Durbuy, La Roche-en-Ardenne and Luxembourg. These however went to a different heir.