| Ireland Drama Festival | Ireland Drama Festival | | | |
| Ibsen- og Hamsun-dagene 2007 | Ibsen- og Hamsun-dagene 2007 | 2007 | 1 | |
| Incorporated Stage Society | Incorporated Stage Society | 1906 | 1 | |
| Innervoice Media | Innervoice Media | 2021 | 1 | |
| Intimes Theater | Intimes Theater | 1909 | 1 | |
| Ibsen Kulturfestival | Ibsen Kulturfestival | 2001 | 1 | |
| International Ibsen | International Ibsen | 2010 | 1 | |
| Internasjonale Figurteaterfestival, Den | Den Internasjonale Figurteaterfestival | 1992 – 1993 | 1 | |
| Ibsen Festival Fringe | Ibsen Festival Fringe | 1992 | 1 | |
| Ibsen 2006 | Ibsen 2006 | 2006 | 1 | |
| Ibsen og Hamsun for ungdom 2006 | Ibsen og Hamsun for ungdom 2006 | 2006 | 1 | |
| Irving Place Company | Irving Place Company | 1917 | 1 | |
| Ibsen- og Hamsun-dagene 2004 | Ibsen- og Hamsun-dagene 2004 | 2004 | 1 | |
| Ibsen- og Hamsun-dagene 2011 | Ibsen- og Hamsun-dagene 2011 | 2011 | 1 | |
| Intercity Festival Oslo | Intercity Festival Oslo | 2009 | 1 | |
| Infamous Commonwealth Theatre | Infamous Commonwealth Theatre | 2011 | 1 | |
| International Ibsen Conference, The | The International Ibsen Conference | 2006 | 1 | |
| Ibsen- og Hamsun-dagene 2008 | Ibsen- og Hamsun-dagene 2008 | 2008 | 1 | |
| Ibsen og Hamsun for ungdom 2007 | Ibsen og Hamsun for ungdom 2007 | 2007 | 1 | |
| Ibsenkvintetten | Ibsenkvintetten | 2006 | 1 | |
| Ibsenjubileet (Ibsen Anniversary) | Ibsenjubileet (Ibsen Anniversary) | 1928 | 1 | |
| Ibsen- og Hamsun-dagene 2012 | Ibsen- og Hamsun-dagene 2012 | 2012 | 1 | |
| Independent Company, The | The Independent Company | 1899 | 1 | |
| Ibsen- og Hamsun-dagene 2003 | Ibsen- og Hamsun-dagene 2003 | 2003 | 1 | |
| Ibsen- og Hamsun-dagene 2010 | Ibsen- og Hamsun-dagene 2010 | 2010 | 1 | |
| ITESM Unidad Chihuahua | ITESM Unidad Chihuahua | 1985 | 1 | |
| Illinois Repertory Theatre University of Illinois | Illinois Repertory Theatre University of Illinois | 1988 | 1 | |
| Institutt for drama/film/teater | Institutt for drama/film/teater | 1994 | 1 | |
| Ibsen- og Hamsun-dagene 2009 | Ibsen- og Hamsun-dagene 2009 | 2009 | 1 | |
| Ibsen- og Hamsun-dagene 2006 | Ibsen- og Hamsun-dagene 2006 | 2005 – 2006 | 2 | |
| Independent Theatre, The | Independent Theatre (The Independent Theatre) | 1946 – 2023 | 2 | |
| Ibsen- og Hamsun-dagene 2013 | Ibsen- og Hamsun-dagene 2013 | 2013 | 2 | |
| IPFW Department of Theatre | IPFW Department of Theatre | 2008 – 2014 | 2 | |
| Ibsen Awards | Ibsen Awards | 2009 – 2019 | 2 | |
| International Theatre Festival | International Theatre Festival | 2004 | 2 | |
| Ibsen Society, The | The Ibsen Society | 1930 | 2 | |
| Ibsen- og Hamsun-dagene 2005 | Ibsen- og Hamsun-dagene 2005 | 2005 | 2 | |
| International Ibsen Festival for University Students | International Ibsen Festival for University Students | 2010 | 3 | |
| International Ibsen Festival 2010 | International Ibsen Festival 2010 | 2010 | 3 | |
| International Ibsen Seminar and Theatre Festival | International Ibsen Seminar and Theatre Festival | 2009 – 2012 | 3 | |
| Indiana University Department of Theatre and Drama | Indiana University Department of Theatre and Drama | 1979 – 2019 | 3 | |
| Internationale Maifestspiele | Internationale Maifestspiele | 1954 – 2003 | 3 | |
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