Ysgol Gyfun Gymraeg Glantaf is a Welsh-medium coeducational secondary school in Llandaff North, a district in the north of Cardiff, Wales; it is the largest of its kind in the country. Of the three Welsh-medium secondary schools serving Cardiff, it was the first to be established; the others are Ysgol Gyfun Gymraeg Plasmawr and Ysgol Gyfun Gymraeg Bro Edern. As of 2017, 36% of pupils came from Welsh-speaking homes.^[1]

Ysgol Gyfun Gymraeg Glantaf was founded in 1978, initially sharing premises with the English-language Glantaf High School, before expanding to occupy the entire building. Its first headmaster was J E Malcolm Thomas, who was succeeded upon his retirement in 1995 by Huw S Thomas, and then by headmistress Rhiannon Lloyd from Rhydywaun School. In early 2010, the board of governors announced that from September 2010, the former head of Rhydywaun School would take over from Rhiannon Lloyd. From September 2010, Alun Davies was headmaster prior to Mathew Evans joining the school in September 2020 as headteacher from Ysgol Gymraeg Ystalyfera Bro Dur.^[2]

Pupil numbers at the school increased into four figures during the mid-1980s, necessitating the annexing of the buildings of the old Waterhall School in Fairwater to form the Ysgol Isaf (Lower School), which housed the first and second forms (later years 7 and 8) of the school from 1986. This split-site arrangement continued until the opening of Cardiff's second Welsh-medium comprehensive school, Ysgol Gyfun Gymraeg Plasmawr, in 1998, from which point the Llandaff North site again housed the entirety of Glantaf's pupils.

Education in Wales differs in certain respects from the systems used elsewhere in the United Kingdom. Ysgol Gyfun Gymraeg Glantaf is a Welsh-medium school, which means that all lessons except English language and literature should take place in the Welsh language. The social use of Welsh is also highly encouraged, in order to ensure the pupils' fluency in the language. Ysgol Glantaf presents sixth form students for the Welsh Baccalaureate examination.

The school's motto is Coron Gwlad Ei Mamiaith, which translates to 'A Country's Crown is Her Mother Tongue'. The school colours are light and dark blue.

The school's four houses are named after Welsh saints: Dewi (house colour: yellow), Dyfrig (green), Illtud (red) and Teilo (blue). The four houses annually compete in the "Gŵyl Glantaf" (Glantaf Festival), in which there is a day of sports and a day of singing, playing instruments, reciting and numerous other events in the theme of the Eisteddfod.

In 2008, 76% of pupils at GCSE (or equivalent) (ages 15 to 16) year achieved 5 or more A* - C grades at GCSE,^[3] and 76% of pupils at A/AS level (or equivalent) (ages 17 to 18) achieved two or more A - C grades.^[3]

In 2019, Ysgol Gyfun Gymraeg Glantaf was named Welsh Secondary School of the year by the Sunday Times.^[4]

Arts and media

• Gareth Bonello, musician
• Huw Bunford, musician, member of Super Furry Animals
• Siân Grigg, BAFTA winner and Oscar nominated Hollywood make up artist
• Ioan Gruffudd, actor
• Ffion Hague, broadcaster and author, wife of Lord William Hague
• Mali Harries, actress
• Gethin Jones, television presenter and former Blue Peter presenter
• Paul Carey Jones, opera singer
• Llwyd Owen, Welsh-language author
• Owen Powell, musician, former member of Catatonia
• Guto Pryce, musician, member of the Super Furry Animals
• Iwan Rheon, actor
• Matthew Rhys, actor
• Huw Stephens, radio presenter and DJ
• Jeremy Huw Williams, opera singer
• Rhodri Williams, sports journalist and television presenter
• Dyfed Wyn-Evans, opera singer

Sport

• Owain Doull, racing cyclist, member of the gold medal-winning team pursuit squad at the 2016 Summer Olympics^[5]
• Ioan Lloyd, Rugby Union, Scarlets & Wales
• Theo Cabango, Rugby Union, Cardiff Rugby
• Seb Davies, Rugby Union, Cardiff Rugby & Wales
• Tom Isaacs, Rugby Union, Ospreys & Cardiff Blues, Rugby Sevens, Wales^[6]
• Darius Jokarzadeh, Olympic weightlifter, represented Wales at the 2014 Commonwealth Games.^[7]
• Manon Johnes, women's Rugby Union, Bristol Bears & Wales
• Max Llewellyn Rugby Union, Gloucester & Wales
• Rhys Patchell, Rugby Union, Highlanders & Wales^[6]
• Jamie Roberts, Rugby Union player, Cardiff Blues & Wales^[6]
• Jamie Robinson, Rugby Union player, Cardiff Blues & Wales
• Nicky Robinson, Rugby Union player, Cardiff Blues & Wales
• Lee Thomas, Rugby Union player, Cardiff Blues^[6]
• Teddy Williams (rugby union), Rugby Union, Cardiff Rugby & Wales

Politics

• Rhys ab Owen, Plaid Cymru Member of the Senedd 2021-
• Eluned Morgan, Labour Party Member of the Senedd 2015-, Welsh Government Minister for Health and Social Services.

• Emyr Currie-Jones, Chairman of the Education Committee of Cardiff City Council, promoted the foundation of the school