1820s in Wales explained

This article is about the particular significance of the decade 1820–1829 to Wales and its people.

Arts and literature

John Elias – Golygiad Ysgrythurol ar Gyfiawnhad Pechadur (1821)
Felicia Hemans – The Forest Sanctuary (1825)
Thomas Price (Carnhuanawc) – An Essay on the Physiognomy and Physiology of the Present Inhabitants of Britain (1829)
David Richards (Dafydd Ionawr) – Cywydd y Dilyw (1821)

John Ellis – Eliot (hymn tune) (1823)
Edward Jones – Hen Ganiadau Cymru (1820)
Peroriaeth Hyfryd (collection of hymns including Caersalem by Robert Edwards) (1827)
Seren Gomer (collection of hymns including Grongar by John Edwards) (1824)

1820
- 21 May – Sir Thomas Lloyd, 1st Baronet, politician and landowner (d. 1877)
1821
- 24 June – Guillermo Rawson, Argentinian politician (d. 1890)
- 16 July – John Jones (Mathetes), preacher and writer (d. 1878)
1822
- 2 March – Michael D. Jones, Patagonian settler (d. 1898)
1823
- 8 January – Alfred Russel Wallace, biologist (d. 1913)
- March – Rowland Williams (Hwfa Môn), poet and archdruid (d. 1905)
- 23 November – Sir John Evans, archaeologist (d. 1908)
1824
- date unknown – John Basson Humffray, political reformer in Australia (d. 1891)
1825
- 7 June – R. D. Blackmore, novelist (d. 1900)
1826
- 13 January – Henry Matthews, 1st Viscount Llandaff (d. 1913)
- 1 March – John Thomas, harpist (d. 1913)
- 8 May – George Osborne Morgan, lawyer (d. 1897)
- 11 May – David Charles Davies, Nonconformist leader (d. 1891)
1827
- 27 October – Joseph Tudor Hughes (Blegwryd), harp prodigy (d. 1841)
1828
- 30 January – John David Jenkins, philanthropist (d. 1876)
1829
- 27 January – Isaac Roberts, astronomer (d. 1904)

1820
- 29 January – King George III of the United Kingdom, Prince of Wales 1751–1760
- 16 June – Thomas Jones of Denbigh, Methodist preacher and writer (b. 1756)
- 27 June – William Lort Mansel, bishop and academic (b. 1753)
- 23 August – John Randles, harpist (b. 1763)
- 28 August – Henry Mills, musician (b. 1757)
1821
- 2 May – Hester Thrale, diarist (b. 1741)
- 7 August – Caroline of Brunswick, former Princess of Wales (1795–1820), 53
1822
- 30 March – David Thomas (Dafydd Ddu Eryri), poet (b. 1759)
- date unknown – Stephen Kemble, actor, brother of Sarah Siddons (b. 1758)
1823
- 26 February – John Philip Kemble, actor, brother of Sarah Siddons (b. 1757)
1825
- 24 February – Thomas Bowdler, editor (b. 1754)
- 9 June – Abraham Rees, encyclopaedist (b. 1743)
- 10 August – Joseph Harris (Gomer), Baptist minister, poet and editor (b. 1773)
1827
- date unknown – Helen Maria Williams, novelist and poet (b. c. 1761)
1828
- September – William Madocks, landowner
1829
- 26 January – Benjamin Millingchamp, collector of manuscripts (b. 1756)
- June – Elizabeth Randles, harpist (b. 1801)