| Camp Bimini | St Pauls |
| Camp Menesetung | Goderich |
| Canada Mortgage and Housing Corporation, Ontario | Toronto |
| Canada. Canada Revenue Agency, Toronto Region | Toronto |
| Canada. Canada Revenue Agency, Toronto Region, Canada Child Benefit | Toronto |
| Canada. Indigenous Services Canada, Indian Residential Schools Resolution Health Support Program (IRSRHSP) | Gatineau |
| Canada. Indigenous Services Canada, Indian Residential Schools Settlement Agreement | Gatineau |
| Canada. Members of Parliament [Central East], Perth Wellington Riding, Federal Constituency Office - Perth-Wellington Riding - John Nater MP | Stratford |
| Canada. Transport Canada, Sarnia, Office of Boating Safety - Pleasure Craft Licences | Sarnia |
| Canada. Transport Canada, Sarnia, Office of Boating Safety - Pleasure Craft Operator Card | Sarnia |
| CanadaHelps | |
| Canadian Alopecia Areata Foundation | King Township |
| Canadian Association of Farm Advisors | Stratford |
| Canadian Bar Association (The), Pro Bono Initiative - Crisis in Ukraine | Ottawa |
| Canadian Baseball Hall of Fame and Museum | St Marys |
| Canadian Cancer Society - Ontario Division, Cancer Information Service | Toronto Downtown North |
| Canadian Centre for Housing Rights, Eviction Prevention and Tenant Services | Toronto |
| Canadian Centre for Rural Creativity | Blyth |
| Canadian Centre to End Human Trafficking, Canadian Human Trafficking Hotline | Ontario |
| Canadian Council on Rehabilitation and Work | Toronto |
| Canadian Environmental Law Association | Toronto |
| Canadian Federation of University Women, Stratford - Mailing Address Only, CFUW Stratford Club | Stratford |
| Canadian Food Inspection Agency, Mitchell District Office, Animals, Importation and Exportation | West Perth |
| Canadian Hearing Services - Toronto and York Region | Toronto |
| Canadian Red Cross, Mailing Address Only, Disaster Management Services | London |
| Canadian Red Cross - Simcoe Muskoka, Simcoe Muskoka Branch, Prevention and Safety, First Aid, CPR, Water Safety, Psychological First Aid | Barrie |
| Canadian Red Cross, Toronto Branch, First Contact Program | Toronto |
| Cancer Care Ontario, Ontario Breast Screening Program | Toronto |
| CarePartners Huron Perth, CarePartners Wingham, Wingham | North Huron |
| CarePartners Huron Perth, Stratford, CarePartners Stratford | Stratford |
| CBEAC - Civic Beautification and Environmental Awareness Committee, No Physical Address | Stratford |
| Cecilia Lara Nutrition Consulting, No Physical Address | Stratford |
| Celebrate Recovery, Elgin Missionary Church | Stratford |
| Central Huron YMCA | Central Huron |
| Centre for Addiction and Mental Health | Toronto |
| Change Her World | Stratford |
| Cheshire, Stratford, Adult Community Assisted Living and Attendant Outreach | Stratford |
| Cheshire, Stratford, Perth Attendant Outreach and Community Assisted Living Services | Stratford |
| Children's Mental Health Ontario | Toronto |
| Chinese and Southeast Asian Legal Clinic, Toronto | Toronto |
| Christian Resource Centre for Huron-Perth Presbytery | West Perth |
| Christopher Leadership Course, No Physical Address | Stratford |
| Chronic Pain, Fibromyalgia, Arthritis and Long Haul COVID Support Group | Goderich |
| CLEAResult Canada, Central East, Enbridge Home Winterproofing and IESO Energy Affordability Programs | Toronto |
| CLEO | Toronto |
| Clothing Loft | North Perth |
| CMHA Huron Perth Addiction and Mental Health Services, Huron County office, CMHA Huron Perth Addiction and Mental Health Services, Goderich | Goderich |
| CMHA Huron Perth Addiction and Mental Health Services, Stratford Connection Centre - St. Paul's Anglican Church, Stratford Connection Centre | Stratford |
| CMHA Huron Perth Addiction and Mental Health Services, Stratford Office - 10 Downie St, CMHA Huron Perth Addiction and Mental Health Services, Stratford | Stratford |
| CMHA Huron Perth Addiction and Mental Health Services, Stratford Office - 10 Downie St, Phoenix Centre & Peer Support | Stratford |
| CMHA Huron Perth Addiction and Mental Health Services, Virtual (phone/Zoom), Crossing Bridges | Stratford |
| CMHA Thames Valley Addiction and Mental Health Services - Huron County Sites, Virtual only, Crossing Bridges | |
| College of Audiologists and Speech Language Pathologists of Ontario | Toronto Downtown North |
| College of Early Childhood Educators | Toronto |
| College of Physicians and Surgeons of Ontario | Toronto Downtown Central |
| College of Psychologists of Ontario (The) | Toronto Downtown North |
| College of Registered Psychotherapists of Ontario | Toronto Downtown |
| Comancheros Car Club, No Physical Address | |
| Community Connection, Free and Low Cost Meals, Central East Ontario | Ontario |
| Community Living North Perth | North Perth |
| Community Living St Marys and Area, St Marys and Area | St Marys |
| Community Living St Marys and Area, Voices Perth, St Marys and Area | St Marys |
| Community Living Stratford and Area | Stratford |
| Community of Christ | Stratford |
| Conestoga College Institute of Technology and Advanced Learning, Academic Upgrading, Stratford Campus | Stratford |
| Conestoga College Institute of Technology and Advanced Learning, Conestoga College Institute of Technology and Advanced Learning, Stratford Campus, Stratford Campus | Stratford |
| Conestoga College Institute of Technology and Advanced Learning, Stratford Campus, CAEC and ACE | Stratford |
| Connecting the Dots for Caregivers, Huron-Perth Counties | Stratford |
| Conservative Party of Canada, Perth - Wellington Conservative Association | Stratford |
| Contact North Huron Bluewater, Contact North Bluewater | Central Huron |
| Countryside Midwifery Services | Perth East |
| Cover Health, Virtual Service, Virtual Walk-In Clinic | Brampton |
| Credit Canada Debt Solutions, Telephone Service | Toronto |
| Cromarty Minor Fastball | West Perth |
| Cystic Fibrosis Canada | Toronto Downtown North |
| Cystic Fibrosis Canada, Huron Oxford Perth Chapter | North Perth |