| 19172 | Adelaide Hospital | TCD MS 11270/6/1-6 | 1866-1998 | 6/ Education Research Instruments Lectures Fees Scho... | Adelaide Hospital Archive |
| 14229 | Alexandra College | | 1866-1916 | 'Alexandra College', 1866-1916, traces the h... | |
| 14230 | Alexandra College | | 1866-1914 | Registers:1866-18741874-18801881-18841884-18891888-1... | |
| 14243 | Alexandra College | | 1866-1872 | Registers, relating to subjects and fees:1866-187218... | |
| 14248 | Alexandra College | | 1866-1902 | Alexandra College and School Balance Sheets, 1866-19... | |
| 14276 | Alexandra College | | 1866-1966 | Centenary Booklet, 1866-1966. | |
| 14277 | Alexandra College | | 1866-1885 | File on the Foundation of the College:Note of the 1s... | |
| 14278 | Alexandra College | | 1866-1870
1872
1874
1891 | 1 file, containing:1st Prospectuses, 1866-1868.1st R... | |
| 14310 | Alexandra College | | 1866-1880 | File on Annie Jellicoe, 1866-1880, including a file ... | |
| 14992 | Armagh Diocesan Archive (RC) | | 1866-1869 | Full lists of these papers are available in the arch... | Archbishop Michael Kieran Archive |
| 16417 | Armagh Diocesan Archive (RC) | | 1852-1866 | Correspondence of Archdeacon Felix Slane to Most Rev... | Most Reverend John Dixon Archive |
| 16221 | Birr Castle Archives | A-W | 1866-1928 | N/8: Box of letters and papers relating to the 6th D... | The Rosse Papers |
| 16223 | Birr Castle Archives | A-W | 1866-1873 | N/8/2-5 3 envelopes of love letters from Hohler to t... | The Rosse Papers |
| 16222 | Birr Castle Archives | A-W | 1866 | N8/1: Small envelope of newspaper cuttings regarding... | The Rosse Papers |
| 16928 | Cashel, Ferns and Ossory Diocesan Archive (CoI) | | 1866-1872 | Among material located in the filing cabinet:(13) A ... | Bolton Library Archive |
| 20696 | Clare County Archives | | 1866-1921 | Reports of the Visiting Committee:June 1866 - July 1... | Kilrush Poor Law Union |
| 16975 | Clare County Archives | | 1866-1921
1899-1925 | Minute Books:August 1899 - July 1900July 1900 - July... | Kilrush Rural District Council |
| 23228 | Cork City and County Archives | U15B/ | 1851-1866 | P/C 219-225 Anne and Thomas Love, 67 Evergreen, Cork... | Thomas Hewitt Papers |
| 23232 | Cork City and County Archives | U395 | 1866 | Settlement on the intermarriage of Joseph Harty with... | Harty Papers |
| 22905 | Cultural Heritage Services Library, Armagh | | 1866 | Rental, maps and descriptive particulars of the land... | |
| 23794 | Delany Archive | Box Bp/12 File JW/1867/ | 1866 | 04: 4 March 1866 SC Propaganda Fide to Bishop James ... | Papers of Dr James Walshe, Bishop of Kildare & Leighlin |
| 23795 | Delany Archive | Box Bp/12 File JW/1867/ | 1866 | 11: 20 October 1866 Sr Angela Murray, Tullow to Bish... | Papers of Dr James Walshe, Bishop of Kildare & Leighlin |
| 3439 | Donegal County Archives | CH/SR/D/10 | 1866-1904 | Abstracts of Accounts:25 March 186625 March 188429 S... | Ballyshannon Poor Law Union |
| 11755 | Donegal County Archives | CH/BV/7/; CH/BV/8/ | 1866-1923 | Minutes (Digitised):Inishowen RDC Minutes, 1899 - 19... | Donegal Rural District Council Records |
| 3136 | Dún Laoghaire-Rathdown County Council | LA1/216 | 1866-1870 | Letters from the Alliance and Dublin Consumers Gas C... | Blackrock |
| 19905 | Erasmus Smith Schools Archives | | 1866-1939 | Letters relating to the Tipperary Grammar School, in... | Erasmus Smith Archives |
| 21912 | Galway Diocesan Archives (RC) | | 1853-1866 | Box 12 Patrick Fallon, bishop of Kilmacduagh and Kil... | |
| 12022 | Kerry Local Studies and Archives Department | SL/B/14 | 1866-1906 | Draft Deeds of Trust for members of the Chute family... | Chute Papers |
| 13185 | Kilmainham Gaol Museum | 07LG-1C45-15 | 1866 | Baptismal certificate of Maria McDonald, December 18... | Easter Week |
| 21150 | King's Hospital School | 232-236A | 1866 | 225F Mercer's Rental, 1866. | King's Hospital Records |
| 21158 | King's Hospital School | 232-236A | 1866-1878 | 231 Account Book, 1866 - 1878. | King's Hospital Records |
| 21209 | King's Hospital School | 5/ | 1866 | 14 Mercers's School Quarterly Abstract of Expenditur... | Mercer's School |
| 1664 | Leitrim Local Studies Department | BG122/A/ | 1866-1880 | Minute Books:31 - July 1866 - February 186732 - Febr... | Mohill Poor Law Union |
| 1665 | Leitrim Local Studies Department | BG122/A/ | 1856-1866 | Minute Books:16 - December 1856 - July 185717 - July... | Mohill Poor Law Union |
| 14150 | Louth County Archives | | 1861-1866 | South Louth Grand Jury Luncheon Lists, 1861 - 1866. | |
| 5674 | Meath Local Studies and Family History Department | BG/128/A/ | 1856-1866 | Minute Books:19 January 1856 - August 185620 August ... | Navan Poor Law Union |
| 5675 | Meath Local Studies and Family History Department | BG/128/A/ | 1866-1876 | Minute Books:39 July 1866 - December 186640 December... | Navan Poor Law Union |
| 22873 | Methodist Historical Society of Ireland | | 1866-1909 | Tullamore and Athlone Methodist Circuit: Names and a... | |
| 3961 | National Archives of Ireland | CSO/ICR 13 | 1866 | Habeas Corpus Suspension Act, 1866: Indexed lists of... | Irish Crimes Records |
| 4852 | National Archives of Ireland | 999/283/1 | 1866 | Agreement for sale by Mary Anne Hill, Royal Terrace,... | House for Fallen Females/Northcote Rescue Home, 1866-1920 |
| 12133 | National Archives of Ireland | CSO/RP/1884/27996 | 1866-1869 | 1 28 Vict cxxxv. An Act for the Better Prevention of... | |
| 12181 | National Archives of Ireland | FileA/242 | 1866 | Includes letter to Sir Thomas from Wodehouse, 3 Apri... | Fenian Papers |
| 952 | National Library of Ireland | Ms11217 | 1866-1868 | Seven documents concerning education in Ireland, 186... | Mayo Papers |
| 1576 | National Library of Ireland | Ms7568 | 1866-1874 | Includes notices of the granting of pensions to Petr... | Larcom papers |
| 1908 | National Library of Ireland | Ms3935 | 1858-1866 | Minute book of the Committee of the New Molyneaux As... | |
| 1913 | National Library of Ireland | Ms4144 | 1860-1866 | A miscellaneous collection of letters to George Rodo... | |
| 1930 | National Library of Ireland | Ms4483 | 1845-1866 | A folder containing some papers of Miss Anne Johnsto... | |
| 1954 | National Library of Ireland | Mss4793-4795 | 1860
1865-1866
1869-1870 | Three journals of Lady Alice Howard which include ac... | Wicklow Papers |
| 2883 | National Library of Ireland | Ms1551 | 1866-1875 | Minutes of the monthly meetings of the Ladies' Sub-C... | |
| 5017 | National Library of Ireland | Ms32609 | 1857-1866 | 57 Book of Sales, 6 June 1857-17 November 1866. | Mendicity Institute |
| 6905 | National Library of Ireland | Ms18902 | 1864-1866 | Three letters to John Barrymore Macnamara, Ennistymo... | Stacpoole Kenny Papers |
| 9092 | National Library of Ireland | Ms14333 | 1859-1866 | Domestic accounts, 1859-1866 [at Dromconora, County ... | O'Loghlen Papers |
| 9699 | National Library of Ireland | Ms17829 | 1866-1869 | Five copies of letters to his parents from J S Casey... | |
| 11637 | National Library of Ireland | Ms12486 | 1865-1866 | Claremorris Poor Law Union Minute Book, 9 September ... | |
| 11638 | National Library of Ireland | Ms12487 | 1866 | Claremorris Poor Law Union Minute Book, 10 March 186... | |
| 11639 | National Library of Ireland | Ms12488 | 1866-1867 | Claremorris Poor Law Union Minute Book, 8 September ... | |
| 4805 | Newtown School, Waterford | School Safe/11 | 1858-1866 | Sub-Committee Reports, 1858-1866. | |
| 4806 | Newtown School, Waterford | School Safe/5 | 1866-1884 | Superintendents' Reports, 1866-1884. | |
| 18971 | Offaly Archives | OCL BG158/7 | 1866 | Rate Return Form. Returns form for Tullamore Union f... | Rate Return Form |
| 8042 | Public Record Office of Northern Ireland | T/1586/1 | 1732-1866 | Pedigree of the Chaine family, Portglenone, 1732-186... | |
| 6368 | Public Record Office of Northern Ireland | T/1769 | 1865-1866
1901 | T/1769/3 Copy of the emigrant diary of Elizabeth An... | |
| 6566 | Public Record Office of Northern Ireland | D/1621 | 1866-c.1940 | c.100 documents relating to the records of Island Sp... | |
| 6725 | Public Record Office of Northern Ireland | D/2053 | 1866-1965 | This collection consists of c.150 documents from Hil... | |
| 6753 | Public Record Office of Northern Ireland | D/2120 | 1866-1967 | Records of Blackstaff Flax Spinning and Weaving Comp... | |
| 6759 | Public Record Office of Northern Ireland | D/2137/ | 1849-1866 | This collection includes, for example: D/2137/1/14B-... | |
| 8182 | Public Record Office of Northern Ireland | T/2007 | 1794-1866 | This collection of documents has been copied from th... | Fitzwilliam Papers |
| 8435 | Public Record Office of Northern Ireland | T/2675 | 1866-1876 | This collection includes: T/2657/2 Copy of a lette... | |
| 8465 | Public Record Office of Northern Ireland | T/2752/ | c.1858-1866 | T/2752/4 A copy of a subscription list towards the p... | |
| 8530 | Public Record Office of Northern Ireland | T/2996/ | 1866-1910 | T/2996/1 Copies of letters from Colonel Edward Saund... | |
| 481 | Religious Society of Friends in Ireland Historical Library | Portfolio 7A | 1715-1866 | 2 Memorandum to George Rooke regarding the lease of... | Handlists/Portfolio |
| 1303 | Religious Society of Friends in Ireland Historical Library | | 1864-1866 | Records: Diary of two walking tours by Susanna Gough... | Museum Collection |
| 1349 | Religious Society of Friends in Ireland Historical Library | Deed Box X | 1794-1866 | Folder 5.18 Bridget Carroll, nee Boylan, Meath Stre... | Deed Boxes, Miscellaneous, New Shelf Head Lists |
| 3872 | Religious Society of Friends in Ireland Historical Library | Mss Box 48 | 1839-1866 | Grubb Collection: Letters from Hannah Grubb to Anne ... | Handlists: Mss Boxes, Pamphlets Boxes, etc. |
| 4157 | Religious Society of Friends in Ireland Historical Library | Deed Box X | 1866 | Bridget Carroll, nee Boylan, Meath Street, Dublin: F... | Deeds |
| 5310 | Religious Society of Friends in Ireland Historical Library | MMIII/J1 | 1866-1878 | Accounts: Accounts of Edenderry Monthly Meeting, 186... | Edenderry Monthly Meeting |
| 11116 | Religious Society of Friends in Ireland Historical Library | MM/XVIB1/Reel 42 | 1866-1879 | Richhill Monthly Meeting, Women's Minutes, 1866-1879... | |
| 21501 | Religious Society of Friends, Ulster Quarterly Meeting Archive | | 1866-1922 | Lisburn proceedings of Quarterly Meetings, 1866-1922... | |
| 2180 | Representative Church Body Library | Ms539 | 1866-1971 | Annual reports, 1866-1868; annual returns, 1938-1971... | Ardfert and Aghadoe Clergy Widows' Fund Society |
| 22070 | Representative Church Body Library | B5 | 1857-1866
1877-1903 | Holy Trinity Parish, Registers of Baptisms:July 1857... | St Fin Barre's Cathedral Cork Archive |
| 22093 | Representative Church Body Library | B10 | 1864
1865
1866
1870 | Diocese of Cork and Ross Visitation Books, Vicar Gen... | St Fin Barre's Cathedral Cork Archive |
| 22097 | Representative Church Body Library | B10 | 1863
1866 | Rural Deans' Reports for the Diocese of Cloyne, ... | St Fin Barre's Cathedral Cork Archive |
| 23687 | Representative Church Body Library | | 1866-1952 | Box 10 Committee Minute Books, Coombe Boys' Home 186... | Mrs Smyly's Homes |
| 23745 | Representative Church Body Library | Ms81/ | 1866-1885 | 7/1-4 Miscellaneous correspondence of Mrs Anne Cathe... | Stopford Family Papers |
| 22394 | Royal College of Physicians of Ireland | | 1866-1948 | Roll of Licentiates in Medicine and Midwifery, 1866-... | Kings and Queens College of Physicians |
| 22428 | Royal College of Physicians of Ireland | | 1866-1895
1947-1960 | Annual Reports:1866-18951947-1960 | Sir Patrick Dun's Hospital |
| 25009 | Royal Irish Academy | 12/K/38 | 1860
1863
1864
1866 | Letters to Mrs Walsh from Bessie Gunning [?], 9 Janu... | J.C. Walker Papers |
| 22442 | Royal Victoria Hospital, Belfast | | 1866-1970 | Student Registers of the Royal Hospital:1866-1916191... | |
| 11968 | St Mary's Hospital, Castlebar | | 1866-1970 | St Mary's Psychiatric Hospital, Castlebar, Count... | |
| 11204 | Trinity College Dublin, Manuscripts and Archives Department | V/123/A | 1859-1866 | Rentals of Tara Hill Estate, 1859-1866. | Courtown Papers |
| 10175 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs7890/9 | 1866
1911 | Childers Photograph Collection, miscellaneous identi... | Erskine Childers Papers |
| 10204 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs9886 | 1866 | Diary of Miss Elsie Burgess, born c1866, fiancée of... | Henry John Allen Papers |
| 10330 | Trinity College Dublin, Manuscripts and Archives Department | V/126/B | 1866-1873 | Rentals of the County Carlow Estate, 1866-1873. | Courtown Papers |
| 11672 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs5235 | 1866-1917 | Incorporated Society for Promoting Protestant School... | Incorporated Society for Promoting Protestant Schools in Ireland |
| 9872 | UCC Special Collections & Archives | BL/EP/G/1511-1537 | 1866-c1911 | Chicester Family Photographs, many undated, 19th and... | Grehan Estate Collection |
| 24116 | Union Theological College | | 1866 | 'Londonderry Presbyterian Bible Women's Mission, 3rd... | Union Theological College Pamphlet Collection |
| 24117 | Union Theological College | | 1866 | 'Presbyterian Orphan Society Provincial Committee Re... | Union Theological College Pamphlet Collection |
| 24179 | Union Theological College | RH-1-224 | 1866-1966 | '100th Annual Report of the Presbyterian Orphan ... | |
| 13845 | University of Galway Archives | A7 | c1838-1866 | The collection includes: Notebooks and papers of Pro... | Richard Doherty Collection |
| 18598 | University of Limerick Special Collections and Archives | P/1 (Section C) | 1813-1866 | Section C: John Fraunceis Eyre FitzGerald (1813-1866... | The Glin Papers |
| 5957 | Waterford City Archives | TNC5/1 | 1838-1866 | Scrap Book: March 1838-. Typescript copies relating... | Records of the Town Clerk |
| 4304 | Westmeath County Archives Department | | 1855-1866 | Rental of the Estate of William Meade Smythe, 1855-1... | Smythe Papers |