| 13078 | Armagh County Museum | | 1820, 1837 | 1988/225 Print, elevation of the Lunatic Asylum for... | |
| 13842 | Armagh County Museum | 1963/107 | c.1820-1852 | Formula book, c.1820-1852, compiled by Dr Meredith A... | |
| 6232 | Ballymoney Library | | 1820-1940 | Soft bound volume of typescript copies of the out-le... | |
| 4486 | Brother Allen Archive | Box 157 | 1820-1855 | 8 Letter to Mrs O'Connell, Cork, from her son, B... | Brother Allen Archival Collection |
| 4247 | Church of Ireland Centre | Ms318 | 1820 | Abstract of gratuities paid to teachers, December 18... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 4268 | Church of Ireland Centre | Serial No11 | 1820 | General Correspondence, II:Lady Louisa Connolly to J... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 4269 | Church of Ireland Centre | Serial No17 | 1820 | General Correspondence, II:Box 2 W. Parnell to Socie... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 18999 | Church of Ireland Centre | Box 36 | 1820 | Model School:Mod. 14 - List of Ladies and Mistresses... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 19002 | Church of Ireland Centre | Box 36 | 1820 | Model School:Mod. 17 - Letter from Ely Le Foru to Mo... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 19005 | Church of Ireland Centre | Box 36 | 1820 | Model School:Mod. 21 - Miss C. Mayne no longer in co... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 19006 | Church of Ireland Centre | Box 36 | 1820 | Model School:Mod. 32 - Extract from Minutes regardin... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 19007 | Church of Ireland Centre | Box 36 | 1820 | Model School:Mod. 33 - Summary of visiting Ladies by... | Records of the Society for Promoting the Education of the Poor of Ireland |
| 19458 | Cloyne Diocesan Archive (RC) | Box D | 1820 | 1791.00/6/1820 Rules of Doneraile General Free-Schoo... | Bishop Copinger |
| 12621 | Cork City and County Archives | | 1820-1880 | General Administration: Correspondence and Documenta... | Youghal Town Records |
| 23822 | Cork City and County Archives | | 1820-1860 | Cork Wide Streets Commissioners drawings and legal m... | Cork City Council Records - Miscellaneous |
| 23666 | Delany Archive | Box Bp/01 File JKL.1821/ | 1820 | 69: October 1820? Copy Doyle to Sr Clare, 4 pages. C... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 23761 | Delany Archive | Box Bp/01 File JKL.1820/ | 1820 | 38: 9 October Doyle, Carlow to Mrs Joseph, Mountrath... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 23762 | Delany Archive | Box Bp/01 File JKL.1820/ | 1820 | 13: 18 February 1820 Doyle, Carlow, to Mrs Joseph, c... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 23763 | Delany Archive | Box Bp/01 File JKL.1820/ | 1820 | 04: 26 January 1820 Doyle, Carlow to Mrs Joseph, con... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 23764 | Delany Archive | Box Bp/01 File JKL.1820/ | 1820 | 02: 19 January 1820 Doyle, Carlow to Rev. Mr Duane, ... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 23765 | Delany Archive | Box Bp/01 File JKL.1820/ | 1820 | 01: 11 January 1820 Bishop K. Marum, Kilkenny to Doy... | Papers of Dr James Doyle, Bishop of Kildare & Leighlin |
| 21906 | Galway Diocesan Archives (RC) | | 1770-1773
1780-1820 | Box 5 Warden John Joyce papers 1770-1773. | |
| 21949 | Galway Diocesan Archives (RC) | | 1780-1820 | Box 6 Manuscript pastorals 1780-1820. | |
| 5067 | Irish Architectural Archive | 97/84/Box 14 | 1780-1820 | Documents, mainly leases relating to lands of Trinit... | Castletown Papers |
| 21716 | Kerry Diocesan Archives (RC) | S71 | 1820 | Propaganda, regarding Bible Society, English Bible i... | Bishop Charles Sugrue, 1797-1825 |
| 21008 | King's Hospital School | 83-99 | 1819-1820 | 92 Agents Accounts, 1819 - 1820. | King's Hospital Records |
| 1074 | Loreto Archives | II | 1820-1861 | Institute history:127 letters from Dr Murray to M. T... | |
| 1075 | Loreto Archives | P2/1 A | 1820-1860 | 127 Letters from Archbishop Murray to M Teresa Ball ... | |
| 4999 | Maynooth University and St Patrick's College, Maynooth | Ms Murphy 44 | 1818-1820 | Translations into Irish from various religious tract... | |
| 20138 | Meath Local Studies and Family History Department | Box F/ | 1820 | 19 Letter to Blossett thanking him for his donation ... | Mountainstown Documents |
| 20183 | Meath Local Studies and Family History Department | Box G/ | 1820 | 4 Deed between John Chambre Earl of Meath and Judith... | Mountainstown Documents |
| 20287 | Meath Local Studies and Family History Department | Box A/ | 1820 | 20 Letter to Arthur Pollock regarding land, 1820. | Mountainstown Documents |
| 20290 | Meath Local Studies and Family History Department | Box A/ | 1820 | 23 Letter to Arthur Pollock regarding Christmas dona... | Mountainstown Documents |
| 20608 | Meath Local Studies and Family History Department | Box E/ | 1820
1875 | 19 Lease to Thomas Russell by Frederick C. Bligh of ... | Mountainstown Documents |
| 8902 | National Archives of Ireland | M6934/16 | c1820 | Minutes of evidence in a case apparently concerning ... | Ballyglunin Papers |
| 8917 | National Archives of Ireland | M3254 | 1820 | Draft or copy Chancery Bill. Hercules Langford Rowle... | Clifden Papers |
| 15327 | National Archives of Ireland | 99/56/5/5 | 1820 | Carhampton Papers. Appointment re. the estate of the... | Family and estate records. 1611-1948 |
| 15339 | National Archives of Ireland | 99/56/9/1/16 | 1820 | Papers relating to Co. Donegal. Assignment of mortga... | Family and estate records. 1611-1948 |
| 15345 | National Archives of Ireland | 99/56/4/5 | 1820 | Papers relating to Co. Donegal. Assignment of mortga... | Family and estate records. 1611-1948 |
| 133 | National Library of Ireland | Ms18430 | 1810-1820 | Typescript of a diary of Anne Jocelyn, Countess of R... | |
| 1582 | National Library of Ireland | Ms3672 | 1820 | Poems of A M Colton of Norton Green presented to his... | |
| 2469 | National Library of Ireland | Ms4714 | 1798-1820 | Account Book of Joshua Carleton, with later entries ... | |
| 2591 | National Library of Ireland | Ms4248 | c1820-1874 | Workmen's and Servants' Wages Book of the estate of ... | |
| 2712 | National Library of Ireland | Ms14121 | 1820 | A 'Christian Remembrancer', 1820, a pocket-book for ... | |
| 2920 | National Library of Ireland | Ms8635 | 1820 | Legal documents concerning the trial of John Scanlon... | |
| 2922 | National Library of Ireland | Ms8647 | 1820-1865 | Documents relating to the O'Beirne family, Jamestown... | O'Beirne Papers |
| 3068 | National Library of Ireland | Ms10169 | c1820 | Photocopy of a list of tenants on the Alcock estate,... | |
| 3069 | National Library of Ireland | Ms10172 | 1791-1820 | Includes, among other documents, letters of Mr and M... | Ussher Papers |
| 3457 | National Library of Ireland | Ms10364 | 1808-1820 | Includes, among other letters, letters to Mrs Sarah ... | Townley Hall Papers |
| 3600 | National Library of Ireland | Mss12180-12185 | c1819-1820 | Six music volumes from the collection of the Stewart... | |
| 8985 | National Library of Ireland | Ms13306 | c1780-1820 | Fifteen letters to the family of Boyle, Earls of Sha... | Shannon Papers |
| 9026 | National Library of Ireland | Ms13748(10) | c1820-1830 | Letters from Lady Anne Fitzpatrick to Richard Wilson... | Fitzpatrick Papers |
| 9192 | National Library of Ireland | Ms14238 | 1817-1820 | Day book of the 12th Viscount Gormanston, 1817-1820,... | Gormanston Papers |
| 9551 | National Library of Ireland | Ms29770(55) | 1820 | Articles of agreement between Mary Doyne, Wingfield ... | Doyne Papers |
| 9631 | National Library of Ireland | Ms27382 | 1820-1823 | Letters from Mrs Rose Delahoyde requesting prompt pa... | O'Bryne Papers |
| 9632 | National Library of Ireland | Ms27338 | 1820-1823 | Letters of Michael Carroll, Urlingford, relaitng to ... | O'Bryne Papers |
| 9763 | National Library of Ireland | Ms18430 | 1810-1820 | Typescript of the diary of Anne Jocelyn, Countess of... | |
| 10667 | National Library of Ireland | Ms16857 | 1820-1872 | Accounts Book of Deborah Manly, Monasteroris, Edende... | |
| 1813 | Public Record Office of Northern Ireland | D/2008 | c.1820-c.1900 | 6 volumes and c.200 miscellaneous Dunn family papers... | |
| 6773 | Public Record Office of Northern Ireland | D/2193/2 | 1820 | Judgement search relating to Helen Montgomery of Lar... | |
| 7166 | Public Record Office of Northern Ireland | D/2995 | 1820-1821 | 3 arithmetic and exercise books of Elizabeth Stewart... | |
| 8429 | Public Record Office of Northern Ireland | T/2662/1 | 1819-1820 | Copy of the journal of Miss Christiana Gordon made w... | |
| 6750 | Public Record Office of Northern Ireland | D/2109 | 1820-1954 | The Duffin papers include, for example: Marriage set... | |
| 7106 | Public Record Office of Northern Ireland | D/2792 | c1820-1950 | The papers of J K Currie and Sons Solicitors, Ballym... | |
| 7450 | Public Record Office of Northern Ireland | D/4073 | 1820-1908 | A detailed calendar of the Armstrong papers is avail... | |
| 7940 | Public Record Office of Northern Ireland | T/1278/1-11 | 1820-1935 | This collection of 11 documents includes an account ... | |
| 1058 | Religious Society of Friends in Ireland Historical Library | Mss Box 22 | 1781-1820 | Extensive list of leases of lands, indentures, power... | Handlists: Mss Boxes, Pamphlets Boxes, etc. |
| 1060 | Religious Society of Friends in Ireland Historical Library | Mss Box 25 | 1775-1820 | Selina ffennell Collection Miscellaneous: Collection... | Handlists: Mss Boxes, Pamphlets Boxes, etc. |
| 3546 | Religious Society of Friends in Ireland Historical Library | MM/XIIZ2/Reel 19 | 1747-1820 | Lisburn Monthly Meeting, Record Book of: Marriages, ... | |
| 3550 | Religious Society of Friends in Ireland Historical Library | MM/XIIK2/Reel 19 | 1820-1856 | Settlement and Removal Register, Lisburn Monthly Mee... | |
| 2209 | Representative Church Body Library | Ms208 | c1820s | Collection contains notes and transcripts in the han... | Letters to John Jebb, Bishop of Limerick |
| 22511 | Royal Society of Antiquaries of Ireland | | 1792-1820 | Book of Brothers, 1792-1820. | Records of the Corporation of Weavers |
| 10362 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs10047/32 | 1820-1871 | Correspondence of Helena Clarrisa (Clara) Graves/Ran... | Graves Papers |
| 10387 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs7619/1-20 | 1811-1820 | Rentals relating to the estate of Sir Robert Gore Bo... | Arran Papers |
| 10423 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs10047/5 | 1812-1820 | Correspondence of Sir Robert Perceval: 1812 1817 181... | Graves Papers |
| 10486 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs3750 | 1820 | Collection of autographs and copies of poems made by... | |
| 10503 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs3402 | 1820-1828 | Peoms of Elizabeth Anne Beresford, later wife of Myl... | O'Reilly Papers |
| 11910 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs10941/2/2 | 1820-1970
1973 | Manuscript and typescript draft text of 'Imagina... | |
| 18471 | UCC Special Collections & Archives | BL/SC/W | 1820-1972 | 6 items, including:2. 9 Dec 1849 Letter to Miss Emma... | Wright Collection |
| 7621 | Ulster University Archive & Special Collections, Coleraine Campus | HAB/G-H | 1734-1820 | HAB/G Genealogical material relating to families in... | H.A. Boyd Papers |
| 18404 | University of Galway Archives | LE21 | 1820 | Soft bound hand-written fair-copy manuscript of an a... | Strickland of County Roscommon |
| 23339 | Waterford City Archives | P15/5/ | 1820 | 8: Manuscript letter from M. Fitzgerald, Knight of G... | Colleen Bawn |
| 23340 | Waterford City Archives | P15/5/ | 1820 | 9: Manuscript letter from M. Fitzgerald, Knight of G... | Colleen Bawn |
| 23341 | Waterford City Archives | P15/5/ | 1820 | 10: Manuscript letter from John. Fitzgerald, (Public... | Colleen Bawn |
| 23342 | Waterford City Archives | P15/5/ | 1820 | 11: manuscript letter from Francis Twiss, Magistrate... | Colleen Bawn |
| 6029 | Westmeath County Archives Department | | 1820-1859 | Housekeeping Account Book, 1820 - 1832. Rentals of ... | |