| Union Presbyterian Church | Georgetown |
| United Senior Citizens of Ontario, Burlington Club 9 - Mailing Address | Burlington |
| United Senior Citizens of Ontario | Toronto |
| Unity Canadian Reformed Church | Burlington |
| University of Toronto, Toronto - Elm St, Faculty of Dentistry, Dental Clinics | Toronto |
| 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 Wheelchairs and Assistive Equipment - Where to Donate, Burlington | Burlington |
| Used Wheelchairs and Assistive Equipment - Where to Donate, Oakville | Oakville |
