Without a shadow of doubt, the single best book I have found for learning Welsh is John T. Bowen and T. J. Rhys’ Teach Yourself Welsh (1970). It is a little dated, but in over thirty brief lessons you are introduced to all the essentials of the language and given simple exercises to practice using what you have learned. I found it useful both for learning Welsh and even for my first year of a Welsh language degree at university.
There is a helpful vocabulary list at the back of the book if you are stuck for a word as well as short story for you to try reading once you have completed the book. Though out of print, you can still obtain second hand copies on Amazon. If you are new to Welsh, I would suggest you begin here. You couldn’t ask for a better introduction to the language. Worth being modernised and reprinted.
Grammar
Bowen, John T. and T. J. Rhys, Teach Yourself Welsh (London, 1970). One of the best introductions to the Welsh language ever written. Within thirty lessons, you will have mastered the essentials of the language and be able to write and speak Welsh confidently. Deserves to be modernised and reprinted.
Ellis, Tony, Y Cyfeiriadur: Cyfeirlyfr i Ddysgwyr Cymraeg, 4th ed. (2015). This is a useful book for learners with an intermediate knowledge of Welsh. The Welsh tends to be northern in dialect, but there is much material useful for learners in both South and North Wales. Contains many helpful lists and examples.
Non Ap Emlyn, Y Chwiliadur Iaith (Aberystwyth, 2002). This was the textbook we used for GCSE Welsh as a second language. Very simple to follow with plenty of examples.
Gramadeg Cymraeg Cyfoes: Contemporary Welsh Grammar, 6th ed. (Llandysul, 2011). This book is particularly useful for those studying A Level Welsh as a second language. It contains all the grammar you are expected to know.
Gruffydd, Heini, Welsh Rules: A Welsh Grammar for Learners (Talybont, 2003). There is also a Welsh Language version of this title called Cymraeg Da (2000). This book is good for beginners and intermediate learners. It contains many useful examples and exercises. However, it is a little bit disorganised and takes a little while to get used to. The explanation of mutations at the beginning is very helpful and thorough.
Hughes, Geraint (ed.), BBC Learn Welsh (Talybont, 2004). This is a very handy little book for learning Welsh produced by the BBC. It is divided into beginners and intermediate/higher levels, so there is content for everyone.
Jenkins, Myrddin, A Welsh Tutor (Cardiff, 1959). An excellent introduction to the written language by the University of Wales Press. A little dated in terms of style. Worth updating and reprinting.
Jones, Morgan D., A Guide to Correct Welsh (Llandysul, 1976). A useful guide to writing correct Welsh. Very concise and to the point. Recommended for intermediate learners.
King, Gareth, Modern Welsh: A Comprehensive Grammar (London & New York, 2016). This is a comprehensive grammar of spoken Welsh. It takes pains to avoid teaching the literary language.
Thomas, Gwyn, Ymarfer Ysgrifennu Cymraeg (Talybont, 2012). This is a useful little book focusing on the written language. It is ideal for those doing A Level Welsh as a first language. I found it helpful during my first year of Welsh at university.
Thomas, Peter Wynn, Gramadeg y Gymraeg (Caerdydd, 1996). This is the standard grammar of the Welsh language, for advanced users only. I found this useful in my second and third years of a university degree in Welsh. It was also helpful when I wrote my MPhil thesis in Welsh. Difficult to master, but worth the effort.
Thorne, David A, A Comprehensive Welsh Grammar (Oxford, 1993). This is a comprehensive Welsh Grammar with hundreds of examples taken from Welsh literature. It is highly organised into numbered sections. There is also a Welsh language version available. This is an advanced grammar for those with some considerable experience of the Welsh language.
Williams, Stephen, J., A Welsh Grammar (Cardiff, 1980). A little dated, but it does what it says on the tin. I would suggest this for intermediate learners of the language.
Dictionaries
Cownie, Alun Rhys, A Dictionary of Welsh and English Idiomatic Phrases (Cardiff, 2001). This is a useful dictionary of idioms – handy for finding just the right phrase. I found it useful for my creative writing module at university.
Cysgeir. This is a collection of dictionaries as part of the Cysgliad package developed by Bangor University. The programme Cysill corrects spelling and grammar, while the dictionary is made up of a collection of various bilingual (Welsh and English) dictionaries. I found this very useful at university for picking up errors when writing essays in Welsh. You can find out more about the programme here: https://www.bangor.ac.uk/canolfanbedwyr/cysgliad_beth_yw_cysgliad.php.en (accessed 31/01/2021).
Evans, H. Meurig and W. O. Thomas (eds), Y Geiriadur Bach: The Welsh Pocket Dictionary (Llandybie, 1959). This is a useful little dictionary to carry around with you as it fits nicely in your pocket. It has a useful list of personal names, place names, animals, birds, fishes, plants and fruits at the back of the dictionary.
Evans, H. Meurig and W. O. Thomas, Y Geiriadur Mawr: The Complete Welsh-English, English-Welsh Dictionary (Llandysul, 1958). This is a standard Welsh dictionary to fit on your shelf at home. Recommended for all levels.
Geiriadur Prifysgol Cymru (GPC). This is the standard dictionary of the Welsh language. It is ridiculously expensive to buy. I found it useful when doing postgraduate study at university. Mercifully, it is available online at http://geiriadur.ac.uk/gpc/gpc.html(accessed 31/01/2021). It offers helpful examples of how a word has been used throughout history.
Griffiths, Bruce, and David Glyn Jones, The Welsh Academy English-Welsh Dictionary (Cardiff, 1995). This is the single best English to Welsh dictionary available. It contains helpful suggestions as to how some words are used in context. We called it ‘Bruce’ at university after the editor. This is definitely a dictionary I would recommend if you are considering an advanced Welsh course or a degree in Welsh. It is available in print or online at https://geiriaduracademi.org (accessed 31/01/2021).
Gruffudd, Heini, The Welsh Learner’s Dictionary (Talybont, 1998). This is an excellent dictionary for Welsh learners. In fact, I would recommend reading the whole dictionary and practise saying the words aloud. It is short enough to work your way through the Welsh to English section systematically. You will have a reasonably good vocabulary once you have mastered this little dictionary.
Gweiadur. This is an online dictionary only (https://www.gweiadur.com/cy/Pawb). It has over 400,000 Welsh words including mutations and verb forms, verbs conjugated in every tense, and audio pronunciation of most words. It is hands down the best online dictionary in the Welsh language.
Lewis, Geraint D., Geiriadur Gomer i’r Ifanc (Llandysul, 1994). Don’t be put off by the title – this is not just for young people. In fact, this is one of the best Welsh dictionaries out there, especially one for giving definitions in Welsh. I found this very useful during my second and third year at university when we were expected to define words in Welsh rather than simply giving the English translation.
Lewis, Geraint D., & Nudd Lewis, Geiriadur Cymraeg Gomer (Llandysul, 2016). This is one of the best Welsh dictionaries money can buy. It takes pains to define words in Welsh. It contains over 45, 000 Welsh definitions and 12, 000 technical terms.
Williams, Carol, What’s The Word for …? Beth yw’r Gair am? (Cardiff, 2002). If you are new to Welsh, I highly recommend this little dictionary for learning your first vocabulary. It is short enough to copy out the words onto flash cards and teach yourself the basic vocabulary it contains. This one is for beginners and children learning Welsh.
Other Helpful Books
Davies, Cennard, Cryno-Ddysg y Cymry: Diarhebion ac Idiomau i Ddysgwyr (Cardiff, 2002). This is a collection of proverbs and idioms in the Welsh language. The proverbs come with a translation, a definition in Welsh, and an example of how they might be used in conversation. I found this very useful during my second year at university when we had to learn Welsh proverbs.
Davies, Cennard, Lluniau Llafar: Idioms for Welsh Learners (Llandysul, 1980). This does what it says on the tin. Introduces a whole range of idioms to expand your language. The idioms come with a translation and an example of use in language.
Edwards, Islwyn D., Cerddi’r Cewri: Casgliad o Gerddi wedi eu Dethol ar gyfer Dysgwyr (Llandysul, 2002). A collection of some of the most famous Welsh poems for learners with vocabulary. This was useful for A Level Welsh as a second language and during my first year at university when studying modern poetry.
Ifans, Rhiannon, Y Golygiadur: Llawlufr i Awduron a Golygyddion (Aberystwyth, 2006). This is a useful book for editors and authors in Welsh. I found it useful for editing my both my undergraduate dissertation and my MPhil dissertation. Ideal for advanced users of the Welsh language.
Jones, Christine M. (ed.), Goreuon y Ganrif: Detholiad o Straeon Byrion I Oedolion sy’n Dysgu’r Gymraeg (Llandysul, 1998). A collection of short stories with vocabulary specifically chosen for learners.
Lewis, D. Geraint, Pa Arddodiad?: A Check-list of Verbal Prepositions, 4th ed. (Llandysul, 2011). D. Geraint Lewis is the author of a number of useful little Welsh books. This is one of the best of them. It explains which prepositions to use following a particular verb. This is a tricky part of Welsh grammar, making this little book a useful reference tool.
Lewis, D. Geraint, Y Llyfr Berfau: A Check-list of Welsh Verbs (Llandysul, 1995). I found this book very useful when I wanted to find how a verb conjugates into a particular tense. It contains a helpful introduction explaining the short form of the verb as well as the periphrastic construction. I found this very useful during my three years at university.
Lewis, D. Geraint, Y Treigladur: A Check-list of Welsh Mutations (Llandysul, 1993). A comprehensive guide to mutations. Worth reading from cover to cover. Useful at all levels.
Stephens, Roy, ac Alan Llwyd, Y Odliadur Newydd (Llandysul, 2008). This is a useful book of rhyming words in Welsh. I found this helpful when writing poetry for my creative writing module during my second and third year at university. If you want to try your hand at writing Welsh poetry, this book is a must have.
Bibles
Beibl.net (2015). This is a translation of the Bible in colloquial Welsh. It is ideal for learners and Welsh speakers alike as the language is quite simple and easy to follow. It available in print and online (http://beibl.net/). Useful for personal devotion, but unlikely to be read in Church on a Sunday.
Y Beibl Canllaw (Bryntirion, 2015). This is a study Bible in Welsh. There are introductions to each book of the Bible and notes on the text. The notes are useful for learners as often they explain the meaning and context of the Welsh.
Y Beibl Cymraeg Newydd: Argraffiad Diwygiedig (2004). This is the Bible in standard written Welsh. Recommended reading if you are looking to write correct formal Welsh. It is much easier to read than the William Morgan translation of 1588.
Y Beibl Cysegr-lân (London, 1992). This is the Bible in traditional Welsh. It is very tricky for beginners to read, but the Welsh is absolutely beautiful for those who can appreciate it.
Y Testament Newydd: The New Testament (Y Beibl Cymraeg Newydd: The English Standard Version) (2004). This is an interlinear translation of the Bible with Welsh in the left-hand column and English in the right. Very useful for Welsh learners as they can pick up any tricky words from the English translation.