Glendower, Owen
or Owain Glyndŵr or Glyn Dŵr
or indeed Owain ap Gruffydd
Proclaimed Prince of Wales on this day 1400.
The anglicised version 'Glendower' is /ɡlɛnˈdaʊə/ (glen DOWer - 'DOW' like 'how')
I look forward to hearing from Welsh speakers for how it's done in Welsh.