Businesses
- Nathaniel Tughan, solicitor
- National Bank Limited
- National Bank of Ireland
- National Cash Register Company Limited
- National Guarantee and Suretyship Association
- National Liberal Club
- National Library
- National Literary Society of Ireland
- National Maternity Hospital
- National Standard and United National Assurance Society
- National Theatre Society
- National Union of Railwaymen
- National University of Ireland
- NC Laundry Limited
- Needham and Fletcher, commission agents
- Nenagh Cooperative Creamery Limited
- Nestlé and Anglo-Swiss Condensed Milk Company
- New Hudson Cycle Company Limited
- Newcomen Ironworks
- Nobbetts Limited, wholesale confectioners
- Nobles and Hoare Limited
- Nolan Brothers
- Nolan's Private Hotel
- Nora Metcalfe, publican
- Norman Dewar, photographer
- Norman Reeves, tailor
- North and Company
- North British and Mercantile Insurance Company
- North City Fish and Fowl Stores
- North City Works
- North Dublin Union
- North of Ireland Produce Company Limited
- Northern Bank
- Nugent's Company Limited
- Nurdin and Peacock
- Nutting and Sons