| Ibsenfestivalen | Ibsenfestivalen (International Ibsen Festival) (Ibsenfestivalen) | 1990 – 2020 | 549 | 3 |
| I Tarocchi - compagnia teatrale | I Tarocchi - compagnia teatrale | 2022 | 4 | 2 |
| Il Mezzogiorno Nuovo D'Italia | Il Mezzogiorno Nuovo D'Italia | 1984 | 1 | 1 |
| Ile Flottante | Ile Flottante | 2013 – 2014 | 3 | 1 |
| Il Teatro della città | Teatro della città | 2019 | 1 | 1 |
| Il Picchio | Il Picchio | 2021 | 1 | 1 |
| Ibseniana-festivalen | Ibseniana-festivalen | 1989 – 2004 | 24 | |
| Ibsen- og Hamsun-dagene 2007 | Ibsen- og Hamsun-dagene 2007 | 2007 | 1 | |
| International Ibsen Stage Festival | International Ibsen Stage (International Ibsen Stage Festival) | 2012 – 2013 | 16 | |
| International Ibsen Festival for University Students | International Ibsen Festival for University Students | 2010 | 3 | |
| Incorporated Stage Society | Incorporated Stage Society | 1906 | 1 | |
| Ibsen- og Hamsun-dagene 2006 | Ibsen- og Hamsun-dagene 2006 | 2005 – 2006 | 2 | |
| Innervoice Media | Innervoice Media | 2021 | 1 | |
| Independent Theatre, The | Independent Theatre (The Independent Theatre) | 1946 – 2023 | 2 | |
| Intimes Theater | Intimes Theater | 1909 | 1 | |
| Ibsen-museet i Grimstad | Ibsen-museet i Grimstad | 2006 – 2007 | 9 | |
| Ibsen- og Hamsun-dagene 2013 | Ibsen- og Hamsun-dagene 2013 | 2013 | 2 | |
| IPFW Department of Theatre | IPFW Department of Theatre | 2008 – 2014 | 2 | |
| Ibsenforbundet | Ibsenforbundet | 2004 – 2007 | 61 | |
| Ingun Bjørnsgaard Prosjekt | Ingun Bjørnsgaard Prosjekt | 2010 – 2014 | 5 | |
| International Ibsen Festival 2010 | International Ibsen Festival 2010 | 2010 | 3 | |
| Ilkley Playhouse | Ilkley Playhouse | 2024 | 1 | |
| Ibsen-Theater aus Berlin, Das | Das Ibsen-Theater aus Berlin | 1901 – 1912 | 60 | |
| Ibsen Kulturfestival | Ibsen Kulturfestival | 2001 | 1 | |
| Ibsen Awards | Ibsen Awards | 2009 – 2019 | 2 | |
| Interzona and La Biennale di Venezia | Interzona (Interzona and La Biennale di Venezia) | 1999 – 2000 | 6 | |
| Isac Fredrik Smitts sällskap | Isac Fredrik Smitts sällskap | 1877 – 1880 | 12 | |
| Internasjonale Figurteaterfestival, Den | Den Internasjonale Figurteaterfestival | 1992 – 1993 | 1 | |
| Ida Müller | Ida Müller | 2007 – 2012 | 8 | |
| Ibsen Festival Fringe | Ibsen Festival Fringe | 1992 | 1 | |
| International Ibsen | International Ibsen | 2010 | 1 | |
| Ibsen Club, The | The Ibsen Club | 1910 – 1911 | 5 | |
| Ibsen 2006 | Ibsen 2006 | 2006 | 1 | |
| Ibsen Scope | Ibsen Scope | 2019 – 2024 | 5 | |
| Ibsen-Ensemble , Das | Das Ibsen-Ensemble | 1906 | 42 | |
| I Nea Skini (Konstantinos Christomanos) | I Nea Skini (Konstantinos Christomanos) | 1901 – 1904 | 13 | |
| Ibsen og Hamsun for ungdom 2006 | Ibsen og Hamsun for ungdom 2006 | 2006 | 1 | |
| Irving Place Company | Irving Place Company | 1917 | 1 | |
| International Ibsen Seminar and Theatre Festival | International Ibsen Seminar and Theatre Festival | 2009 – 2012 | 3 | |
| Ibsen- og Hamsun-dagene 2004 | Ibsen- og Hamsun-dagene 2004 | 2004 | 1 | |
| Ibsen- og Hamsun-dagene 2011 | Ibsen- og Hamsun-dagene 2011 | 2011 | 1 | |
| Indiana University Department of Theatre and Drama | Indiana University Department of Theatre and Drama | 1979 – 2019 | 3 | |
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