Bro Myrddin Welsh Comprehensive School
|Motto||Heb Ddysg Heb Ddeall (Without learning there is no understanding)|
|Headteacher||Dr Llinos Jones|
|Chairman of Governors||Mr Gareth Jones|
|Local authority||Carmarthenshire County Council|
|Houses||Hengwrt, Hergest , Llwydiarth and Peniarth|
|Colours||Lilac and Black|
Ysgol Gyfun Gymraeg Bro Myrddin (English: Bro Myrddin Welsh Comprehensive School) is a Welsh-medium school in Carmarthenshire, Wales. It is situated near the village of Croesyceiliog, about 2 km south of Carmarthen. Myrddin, the Welsh name of the legendary figure Merlin, is traditionally associated with the town of Carmarthen (Caerfyrddin: Myrddin's fort), and Bro Myrddin means "Myrddin's country (or vale)".
Approximately 79% of pupils come from Welsh-speaking homes, but all pupils speak Welsh to first-language standard.
The School was founded in 1978, on the premises of the former Queen Elizabeth's Grammar School for Boys, Carmarthen. In 1996 the school was moved to its current purpose built campus at Croesyceiliog. Its first Pennaeth (Headteacher) was Mr Gareth Evans, who was succeeded upon his retirement in 1997 by Mr Eric Jones, and then by Mr Dorian Williams, in 2006. The latest Headteacher is Dr Llinos Jones, who took Mr Williams' place at his retirement in 2014.
The school's motto is 'Heb Ddysg Heb Ddeall', which translates as 'Without learning there is no understanding'. The school colours are lilac and black.
The school has four houses (which are referred to using the Welsh 'Llys'): Hengwrt (house colour: green), Hergest (red), Llwydiarth (black) and Peniarth (blue). The four houses annually compete in the school's own version of the Eisteddfod, in which there is a day of singing, playing instruments, reciting and numerous other events – held on the nearest Friday to St David’s day, and a sports day held in the summer term, also numerous events are held during the year.
Every approximately 3 years a musical is performed in the local theater. The 2016 musical was called 'Chwarae Cuddio' (hide and seek in welsh). This is a modern story which looks at how young people play hide and seek on social networking websites. 
2007: 82.8% of 15-year-old pupils achieved 5 or more A* - C grades at GCSE or equivalent
2007: 81.9% of 17-year-old pupils achieved 2 or more A - C grades at A/AS level or equivalent
2015: 81.7% of 15-year-old pupils achieved 5 or more A* - C grades at GCSE
- Core: Welsh, Maths, English and Science
- Humanities: History, Geography, and Religious Studies
- Creative subjects: Drama, Art and Design, and Music
- Technology: ICT, Resistant Materials, Catering, Health and Social Care, Textiles, Furniture *Manufacture and Graphic products
- Foreign languages: French, German, or Spanish
Other: Business Studies
- Llyr Huws Gruffydd Welsh politician
Acting, music and literature
- Euros Childs Musician, member of Gorky's Zygotic Mynci
- John Lawrence (musician) Musician, member of Gorky's Zygotic Mynci
- Richard James (musician) Musician, member of Gorky's Zygotic Mynci
- Stephen Jones (rugby player) Rugby Union player, Llanelli Scarlets & Wales national rugby union team
- Rhys Priestland Rugby Union player, Llanelli Scarlets
- Ken Owens Rugby Union player, Llanelli Scarlets
- Aled Thomas Rugby Union & Rugby Union Sevens player London Welsh, Wales national rugby sevens team
- Matthew Stevens professional snooker player
- Mefin Davies Rugby Union player, Leicester Tigers & Wales national rugby union team
- Rhydian Jones - Footballer, CPD Y GSE & Scouting For Goals
- Elin Llwyd Actress & Singer, notably played Katie on S4C's Pobol Y Cwm
- Tudur Phillips Presenter on S4C's Uned 5
- Gwenan Thomas - Presenter on S4C children's TV show 'Mosgito'
- Catrin Lisa Davies - Actress on S4C's 'Teulu'
- Elis James - Comedian, TV Show Panelist
- Aled Davies - Actor, played Rhys in S4C's Pobol Y Cwm
- "Ysgol Gyfun Gymraeg Bro Myrddin | Estyn". www.estyn.gov.wales. Retrieved 2016-09-24.
- Ysgol Gyfun Gymraeg Bro Myrddin web site (in Welsh)