This bilingual book provides a detailed overview of the project to construct a National Corpus of Contemporary Welsh (CorCenCC), addressing the conceptual and methodological challenges faced when developing language corpora for minoritised languages. A conceptual framework is presented for the user-driven design that underpinned the CorCenCC project, along with a detailed blueprint that can function as a scaffold for other researchers embarking on projects of this nature. This book will be of value to those working in language teaching, learning and assessment, language policy and planning, translation, corpus linguistics and language technology, and to anyone with an interest in Welsh and other minoritised languages. Maer llyfr dwyieithog hwn yn rhoi trosolwg manwl or prosiect i greu Corpws Cenedlaethol Cymraeg Cyfoes (CorCenCC), ac yn mynd ir afael âr heriau cysyniadol a methodolegol a wynebir wrth ddatblygu corpora iaith ar gyfer ieithoedd lleiafrifoledig. Cyflwynir fframwaith cysyniadol ar gyfer y cynllun wedii yrru gan ddefnyddwyr syn greiddiol i brosiect CorCenCC, ynghyd â glasbrint manwl a all weithredu fel sgaffald i ymchwilwyr eraill syn dechrau ar brosiectau or fath. Bydd y llyfr hwn o werth ir rhai syn gweithio ym meysydd addysgu, dysgu ac asesu ieithoedd, polisi iaith a chynllunio ieithyddol, cyfieithu, ieithyddiaeth gorpws a thechnoleg iaith, ac unrhyw un â diddordeb yn y Gymraeg ac ieithoedd lleiafrifoledig eraill.