| UNICEF Canada, Programs and Services | Toronto |
| Union Presbyterian Church | Georgetown |
| United Senior Citizens of Ontario, Burlington Club 9 - Mailing Address | Burlington |
| United Senior Citizens of Ontario | Toronto |
| United Way Golden Horseshoe, Halton & Hamilton - Head Office | Burlington |
| Unity Canadian Reformed Church | Burlington |
| University of Toronto, Division of Anatomy, Body Donation Program | Toronto |
| University of Toronto, Comparative Education Service | Toronto |
| University of Toronto, Toronto - Elm St, Faculty of Dentistry, Dental Clinics | Toronto |
| Unsinkable, Mental Health Support and Awareness | Toronto |
| Unsinkable, Unsinkable Youth | Oakville |
| Upper Credit Humane Society, Thrift Shop | Georgetown |
| Uptown Medical, Family Practice and Walk-in Clinic | Oakville |
| Uptown Medical Pharmacy, Pharmacy Services | Oakville |
| Urge To Purge, Hoarding Remediation Services | Welland |
| Urgent Care Pharmacy, Pharmacy Services | Halton Hills |
| UrgentCareOntario.ca, Online, Virtual Urgent Care for adults | Ontario |
| UrgentCareOntario.ca, Online, Virtual Urgent Care for Children | Ontario |
| Urology Resource Centre | Burlington |
| Used Appliances, Clothing, Furniture, and Household Goods - Where to Donate, Burlington | Burlington |
| Used Appliances, Clothing, Furniture, and Household Goods - Where to Donate, Milton | Milton |
| Used Appliances, Clothing, Furniture, and Household Goods - Where to Donate, Oakville | Oakville |
| Used Books - Where to Donate, Burlington | Burlington |
| Used Books - Where to Donate, Milton | Milton |
| Used Books - Where to Donate, Oakville | Oakville |
| Used Cars - Where to Donate, Burlington | Burlington |
| Used Computers, Electronics, Batteries and Cell Phones - Reuse and Recycling, Burlington | Halton Region |
| Used Computers, Electronics, Batteries and Cell Phones - Reuse and Recycling, Oakville | Oakville |
| Used Eyeglasses - Where to Donate, Halton Region | Halton Region |
| Used Wheelchairs and Assistive Equipment - Where to Donate, Burlington | Burlington |
| Used Wheelchairs and Assistive Equipment - Where to Donate, Oakville | Oakville |
