| 4510 | Brother Allen Archive | Box 211 | 1803-1868 | Diary of Ms Penella Lenigan of Castle Fogarty, 1843.... | Brother Allen Archival Collection |
| 16800 | Cashel, Ferns and Ossory Diocesan Archive (CoI) | | 1803-1877 | Register of Baptisms, 1809; marriages, 1804-1845; bu... | Bolton Library Archive |
| 17041 | Cloyne Diocesan Archive (RC) | Box F | 1803 | 1791.00/3/1803 Letter from Count Bearhaven, Madrid t... | Bishop W. Coppinger |
| 17209 | Cloyne Diocesan Archive (RC) | Box S | 1803
1861 | 1796.05/100/1861 Letter from Revd. J Fitzpatrick, M... | Bishop W. Keane Papers |
| 24527 | Hunt Museum | | 1803 | The Artist and his Wife by Robert Fagan, c.1803. | |
| 5083 | Irish Architectural Archive | 97/84/Box 28 | 1728-1803 | Documents, mainly legal in nature and relating to Le... | Castletown Papers |
| 5112 | Irish Architectural Archive | 97/84/Box 80 | 1759-1803 | Account Books and papers relating to Castletown esta... | Castletown Papers |
| 5108 | Irish Architectural Archive | 97/84/Box 74 | 1624-1803 | Legal documents including marriage settlement referr... | Castletown Papers |
| 5109 | Irish Architectural Archive | 97/84/Box 76 | 1720-1803 | Documents, such as letters and accounts mainly relat... | Castletown Papers |
| 13051 | Kilmainham Gaol Museum | 2PC-1A41-8 | 1803 | Section of a page of a Kilmainham register for 1803 ... | 1803 Rebellion |
| 19037 | Limerick Archives | P21 | 1803-1843 | Notebooks containing personal expenditure, housekeep... | Coote Papers |
| 5753 | Maynooth University and St Patrick's College, Maynooth | | 1798-1803 | Letters of Eugene Conwell: Large bound volume with l... | Conwell Letters |
| 22891 | Methodist Historical Society of Ireland | | 1803-1846
1934 | 27 archival boxes containing letters, pamphlets, pic... | |
| 3947 | National Archives of Ireland | 620/66 | 1803 | 260 Russell, Margaret to the Right Honorable Willia... | Rebellion Papers |
| 3952 | National Archives of Ireland | Soc1025/31 | 1803 | Series 1: Ballinqarane, County Limerick, information... | State of the Country Papers |
| 8900 | National Archives of Ireland | M6934/1 | 1803-1813 | Mary Blake, (nee Archdeacon, widow of Walter Blake o... | Ballyglunin Papers |
| 11444 | National Archives of Ireland | | 1803
1821 | Letter from Custom Officials relating to the petitio... | Customs and Excise |
| 15208 | National Archives of Ireland | 97/36 | 1803-1818 | St Paul's Parish, St Nicholas's Parish, Carrigaline ... | Selection of Private Accessions, 1980-2002 |
| 173 | National Library of Ireland | Ms18752 | 1803 | Diary of Maria Edgeworth, with references to politic... | |
| 2321 | National Library of Ireland | Ms8326 | 1806-1808
1803
1954 | Typescript copies of the letters of Sarah Curran, Mr... | Sarah Curran papers |
| 2446 | National Library of Ireland | Mss9553-9554 | 1803-1817 | Two brief Diaries [?of Mrs Balfour], covering the pe... | Townley Hall Papers |
| 2713 | National Library of Ireland | Mss14338-14341 | 1803-1819 | Four Ledgers of miscellaneous accounts of Lady Louis... | |
| 2967 | National Library of Ireland | Ms8905 | 1803-1816 | Miscellaneous letters and documents, 1803-1816. Thes... | |
| 2990 | National Library of Ireland | Ms9216 | 1803-1823 | An incomplete Account Book of the Sick Poor Institut... | |
| 3043 | National Library of Ireland | Ms9941 | 1803-1827 | Rent Ledger of the estate of Stewart Weldon in the A... | Weldon Papers |
| 3067 | National Library of Ireland | Ms10162 | 1803 | Rental of the estate of Ponsonby Tottenham, County L... | Pakenham-Mahon Papers |
| 3494 | National Library of Ireland | Ms10947 | 1626-1803 | Photostat copy of a register of births, deaths and m... | |
| 3512 | National Library of Ireland | Ms11055 | 1803-1819 | Miscellaneous letters, including letters to, or con... | Ormonde Papers |
| 3724 | National Library of Ireland | Ms12993 | 1803-1826 | Records of expenditures by William Gun Paul as execu... | |
| 9173 | National Library of Ireland | Ms15145 | 1803-1835 | Eight letters to William Kemmis, Crown Solicitor, 18... | Kemmis Papers |
| 9179 | National Library of Ireland | Ms15161 | 1803-1923 | Rentals of the Kemmis estates in County Wicklow: 180... | Kemmis Papers |
| 9676 | National Library of Ireland | Ms29806(188-189) | 1803 | Ms29,806(188) Marriage settlement of Elizabeth, eld... | Dunalley Papers |
| 10093 | National Library of Ireland | Ms16354(81) | 1803 | Mrs Anna Worsley to Lord Bolton, soliciting a promot... | Bolton Manuscripts |
| 10656 | National Library of Ireland | Ms16233 | 1793-1803 | Dublin Tholsel Grand Jury Presentment Book, includes... | |
| 11043 | National Library of Ireland | Ms18752 | 1803 | Diary of Maria Edgeworth with references to politica... | |
| 11068 | National Library of Ireland | Ms19189-19190 | 1803-1813 | Rentals and accounts of the estate of Viscount Power... | Powerscourt Papers |
| 7219 | Public Record Office of Northern Ireland | D/3139 | 1803-1841 | Household account book kept by Mrs William Tennent, ... | |
| 7506 | Public Record Office of Northern Ireland | D/572/12 | 1792-1803 | Volume of ladies' letters to Earl Macartney, som... | Macartney Papers |
| 7763 | Public Record Office of Northern Ireland | MIC/257 | 1803 | Microfilmed copy of a letter from Lord Castlereagh t... | |
| 8370 | Public Record Office of Northern Ireland | T/2542/1 | 1803 | Copy of a letter from Admiral Lord Nelson aboard the... | |
| 8498 | Public Record Office of Northern Ireland | T/2872/ | 1763-1803 | T/2872/6 A copy of a letter from Lady Bandon to Lord... | Alnwick Papers |
| 8551 | Public Record Office of Northern Ireland | T/316/5 | 1803 | Copy of a bond from William Bristow, Vicar General o... | |
| 3562 | Religious Society of Friends in Ireland Historical Library | MM/XIIIB2/Reel 29A | 1796-1803 | Women's Minutes, Lurgan Monthly Meeting, 1796-1803. ... | |
| 4166 | Religious Society of Friends in Ireland Historical Library | Deed Box XII | 1803-1804 | Elizabeth Cope, wife of William Cope: Folder 9:3 Pa... | Deeds |
| 4112 | Royal Irish Academy | 12/R/23-26 | 1774-1803 | Letters to A H Haliday: 12/R/23 Volume 1, 1782-1793... | James, Earl of Charlemont Correspondence |
| 4113 | Royal Irish Academy | 12/M/8 | 1803 | Rising of 1803, Depositions: Volume of depositions r... | Halliday Collection |
| 6453 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs5445a | 1803-1807 | Incorporated Society for Promoting Protestant School... | Incorporated Society for Promoting Protestant Schools in Ireland |
| 10259 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs3524 | 1772-1803 | Commonplace Book of verse belonging to Sarah and Tho... | Shackleton Family Papers |
| 10427 | Trinity College Dublin, Manuscripts and Archives Department | TCDMs10047/21 | 1803-1836 | Correspondence of Helena Perceval with her family, t... | Graves Papers |
| 11677 | Trinity College Dublin, Manuscripts and Archives Department | TCDMss5273-5284 | 1803-1825 | Incorporated Society for Promoting Protestant School... | Incorporated Society for Promoting Protestant Schools in Ireland |
| 18765 | Trinity College Dublin, Manuscripts and Archives Department | TCD MS 9308/822 | 1803 | Mrs Lynch's depostiton outlines a sexual assault and... | 'Q' Company Dublin Brigade Old IRA |