| IAVGO Community Legal Clinic | Toronto |
| Ideal Chiropractic | Barrie |
| Ideal Rebekah Lodge 199 | Midland |
| Iglesia Pentecostal LaSenda, Barrie | Barrie |
| Imani's Place Foundation | New Tecumseth |
| Immaculate Conception Roman Catholic Church, Alliston | New Tecumseth |
| In Search of Justice, No Physical Address | Vaughan |
| In Support Of Children Counselling, Unpublished, Counselling Services | Collingwood |
| Inclusion Northumberland, Campbellford - Bridge St E, Administration | Campbellford |
| Inclusion Northumberland, Campbellford - Bridge St E, Campbellford Community Respite | Campbellford |
| Inclusion Northumberland, Campbellford Community Resource Centre, Campbellford - Bridge St E | Campbellford |
| Inclusion Northumberland, Community Homes, Campbellford - Bridge St E | Campbellford |
| Inclusion Northumberland, Individual Residential Care Program, Campbellford - Bridge St E | Campbellford |
| Inclusion Northumberland, LifeShare, Campbellford - Bridge St E | Campbellford |
| Inclusion Northumberland, Passport Funding, Campbellford - Bridge St E | Campbellford |
| Inclusion Northumberland, Supportive Independent Living, Campbellford - Bridge St E | Campbellford |
| Inclusive Milestones Child Development Centres, Clinical Services | Barrie |
| Inclusive Milestones Child Development Centres, Educational Services | Barrie |
| Inclusive Milestones Child Development Centres, Recreation Services | Barrie |
| Income Security Advocacy Centre | Toronto |
| Independent Electricity System Operator, Mailing Address, saveONenergy Program | Barrie |
| Independent First Nations, Grey Bruce, Mobile Service, Jordan's Principle Navigator Program | Saugeen Shores |
| Independent Grocer Loblaws Pharmacy, Christmas Dinner, Bracebridge | Bracebridge |
| Independent Living Services Simcoe County | Barrie |
| Independent Living Services Simcoe County, Accessibility, Resources and Connections | Barrie |
| Independent Living Services Simcoe County, Assisted Living Services for Seniors | Barrie |
| Independent Living Services Simcoe County, Barrie, Community Development and Training and Consultation | Barrie |
| Independent Living Services Simcoe County, Barrie, Homemaking Program | Barrie |
| Independent Living Services Simcoe County, Barrie | Barrie |
| Independent Living Services Simcoe County, Personal Support Services | Barrie |
| Independent Living Services Simcoe County, Online / Web Service, Quipit | Barrie |
| Independent Order of Odd Fellows, Exeter, Lodge 67 | Exeter |
| Independent Order of Odd Fellows, Stratford - The Grand Lodge of Ontario, Avon Lodge #41 | Stratford |
| Independent Order of Odd Fellows and Rebekah's, Cobourg Memorial Temple | Cobourg |
| Independent Order of Odd Fellows Campbellford Lodge 248 | Trent Hills |
| Indian River Reptile Zoo | Otonabee-South Monaghan |
| Indigenous Diabetes Health Circle, Central Region, Indigenous Diabetes Health Circle Central Region | Barrie |
| Indigenous Diabetes Health Circle, Head Office, Mailing Address, Indigenous Diabetes Health Circle, Curve Lake | |
| Information and Privacy Commissioner of Ontario | Toronto Downtown |
| Information on the Total Solar Eclipse 2024 | Ontario |
| Information Orillia, Orillia Public Library, Income Tax Clinic | Orillia |
| Information Orillia, Orillia Public Library | Orillia |
| Information Orillia, Orillia Public Library, Orillia Volunteer Centre | Orillia |
| Inglenook Creche Childcare Centre | Owen Sound |
| Inner Growth Counselling & Psychotherapy | Barrie |
| Innisfil Community Church | Innisfil |
| Innisfil Community Church, Innisfil Food Bank | Innisfil |
| Innisfil Historical Society | Innisfil |
| Innisfil ideaLAB & Library, Cookstown Branch | Innisfil |
| Innisfil ideaLAB & Library, Lakeshore Branch | Innisfil |
| Innisfil ideaLAB & Library, Stroud Branch | Innisfil |
| Innisfil Taxi | Innisfil |
| Innisfil. Fire and Rescue Service | Innisfil |
| Institute for Advancements in Mental Health | Toronto |
| Insurance Bureau of Canada, Ontario Head Office, Consumer Information Centre | Toronto |
| Integrated Autism Consulting, Barrie | Barrie |
| Intelligent Elders Club (The) | Orillia |
| Interfaith Northumberland | Cobourg |
| International Brotherhood of Electrical Workers, Barrie Office, Local 353 | Barrie |
| International Order of Alhambra, Grand Bend, Algarva 168 Caravan | Lambton Shores |
| International Pen Friends | Orillia |
| International Union of Operating Engineers, No Physical Address, Local 793 | Barrie |
| Intyre Electronic Recycling | Huntsville |
| IODE, Festival Jubilee Chapter | Stratford |
| IODE- Maple Leaf Chapter, Goderich | Goderich |
| IOOF Seniors Homes | Barrie |
| IOOF Seniors Homes, Barrie - 10 Brooks St, Odd Fellow and Rebekah Home | Barrie |
| IOOF Seniors Homes, Barrie - 20 Brooks St, Heritage Place | Barrie |
| IOOF Seniors Homes, Barrie - 90, 92, 94 Dean Ave, The Terraces at Heritage Square | Barrie |
| IPIC Education and Counselling Services | Stratford |
| Irish Claddagh Club of Barrie and District | Barrie |
| It Takes a Village | North Perth |
| Itosu Kai Karate Collingwood | Collingwood |
| It's Personal Period | Chesley |