Coordinates: 51°48′58″N 3°22′05″W / 51.816°N 3.368°W / 51.816; -3.368

Mid Glamorgan (Welsh: Morgannwg Ganol) is a preserved county of Wales. From 1974 until 1996, it was also an administrative county, with a county council.

Mid Glamorgan was formed in 1974 under the Local Government Act 1972. It consisted of part of the former administrative county of Glamorgan, and the county borough of Merthyr Tydfil, along with the parishes of Penderyn and Vaynor from Brecknockshire and the urban districts of Bedwas and Machen, Rhymney and part of Bedwellty, from Monmouthshire.

It was divided into six districts:

Mid Glamorgan and its component districts were abolished in 1996 and the area split into the unitary authorities of Bridgend, Merthyr Tydfil, Rhondda Cynon Taf and part of Caerphilly as a result of the Local Government (Wales) Act 1994.

The communities of Wick, St Brides Major, Ewenny (from the Ogwr district) became part of the Vale of Glamorgan county borough, while Pentyrch (from the Taff-Ely district) was added to the Cardiff unitary authority area. Because of this, they became part of the preserved county of South Glamorgan. In 2003 the ceremonial borders were further adjusted, placing the entire Caerphilly county borough in the ceremonial county of Gwent.

Glamorgan or Glamorganshire (Welsh: Morgannwg [mɔrˈɡanʊɡ] or Welsh: Sir Forgannwg [ˈsiːr vɔrˈɡanʊɡ]) is one of the thirteen historic counties and a former administrative county of Wales. It was originally an early medieval kingdom of varying boundaries known as Glywysing until taken over by the Normans as a lordship. Glamorgan is latterly represented by the three preserved counties of West Glamorgan, Mid Glamorgan and South Glamorgan. The name also survives in that of the county borough of the Vale of Glamorgan.

Although initially a rural and pastoral area of little value, the area that became known as Glamorgan was a conflict point between the Norman lords and the Welsh princes, with the area being defined by a large concentration of castles. After falling under English rule in the 16th century, Glamorgan became a more stable county, and exploited its natural resources to become an important part of the Industrial Revolution. Glamorgan was the most populous and industrialised county in Wales and was once called the 'crucible of the Industrial Revolution', containing the world centres of three metallurgical industries, and its rich resources of coal.