The Isle of Anglesey (99.1%), Caerphilly (98.8%), and Pembrokeshire (98.6%) had the highest proportions of people whose main language was English or Welsh in 2021.
Roedd y cyfrannau uchaf o bobl a oedd wedi nodi Cymraeg neu Saesneg fel eu prif iaith yn 2021 yn Ynys Môn (99.1%), Caerffili (98.8%), a Sir Benfro (98.6%).