| Sør-Trøndelag County Municipality | |
| Native Name: | Sør-Trøndelag fylkeskommune |
| Settlement Type: | County |
| Subdivision Type: | Country |
| Subdivision Name: | Norway |
| Seat Type: | Administrative center |
| Seat: | Trondheim |
| Leader Title: | County mayor |
| Leader Name: | Tore O. Sandvik |
| Leader Title1: | Chairman of Cabinet |
| Iso Code: | NO-16 |
| Blank Name Sec1: | Revenue |
| Blank Info Sec1: | NOK 2,500 million |
| Blank1 Name Sec1: | Employees |
| Blank1 Info Sec1: | 2,600 |
| Blank Name Sec2: | Schools |
| Blank Info Sec2: | 24 |
| Blank1 Name Sec2: | Pupils |
| Blank1 Info Sec2: | 10,000 |
| Blank2 Name Sec2: | Transit authority |
| Blank2 Info Sec2: | None |
| Blank3 Name Sec2: | Roads |
Sør-Trøndelag County Municipality (Norwegian: Sør-Trøndelag fylkeskommune) was the regional governing administration of the old Sør-Trøndelag county in Norway until 1 January 2018 when it merged with Nord-Trøndelag county to form the new Trøndelag county. The main responsibilities of the county municipality included the running of 25 upper secondary schools. It administered the county roadways, public transport, dental care, culture, and cultural heritage.
The Sør-Trøndelag county council (Norwegian: Fylkestinget) is made up of 37 representatives that were elected every four years. The council essentially acted as a Parliament or legislative body for the county and it met several times each year. The council is divided into standing committees and an executive board (Norwegian: fylkesutvalg) which meet considerably more often. Both the council and executive board are led by the County Mayor (Norwegian: fylkesordfører) who held the executive powers of the county. Prior to its dissolution, the county mayor was Tore O. Sandvik (Labour) while his deputy was Arne Braut (Centre Party).
The party breakdown of the council was as follows:
Public transport in the county was operated on public service obligation contracts from the county municipality via the transportation authority company AtB AS (meaning A to B) (web site), and operations are performed by Boreal Buss, Nettbuss, Tide Buss and TrønderBilene (buses), Boreal Bane (tram), and Fosen Trafikklag and Kystekspressen (passenger ferries). County road are operated by the Norwegian Public Roads Administration, though managed by the county municipality.