| 4,201 | olheiser.ca | — | | 1/11 |
| 4,202 | omnimca.ca | Finance / banking / insurance | niche | 1/11 |
| 4,203 | onclebill.ca | — | keyword | 1/11 |
| 4,204 | ondeckmarine.ca | General services (cleaning, plumbing, contractors) | keyword | 1/11 |
| 4,205 | ondemandlawncare.ca | General services (cleaning, plumbing, contractors) | keyword | 1/11 |
| 4,206 | one60elgin.ca | — | | 1/11 |
| 4,207 | one8cafe.ca | Food / restaurant / beverage | keyword | 1/11 |
| 4,208 | onebbq.ca | Food / restaurant / beverage | keyword | 1/11 |
| 4,209 | oneearthblog.ca | — | keyword | 1/11 |
| 4,210 | onestopsantashop.ca | Retail / e-commerce / shop | keyword | 1/11 |
| 4,211 | onlineguardtraining.ca | Fitness / sports / outdoor | keyword | 1/11 |
| 4,212 | onrecords.ca | — | word | 1/11 |
| 4,213 | ontariocricketassociation.ca | Fitness / sports / outdoor | niche | 1/11 |
| 4,214 | ontariopsychologists.ca | Healthcare / medical / mental health | keyword | 1/11 |
| 4,215 | ontariostudenthousing.ca | — | | 1/11 |
| 4,216 | ontariovineyards.ca | Food / restaurant / beverage | geo | 1/11 |
| 4,217 | openmindsonly.ca | — | keyword | 1/11 |
| 4,218 | opportunitiesnorth.ca | Jobs / careers / HR | keyword | 1/11 |
| 4,219 | oprintz.ca | — | brandable | 1/11 |
| 4,220 | oratii.ca | — | brandable | 1/11 |
| 4,221 | orcdsb.ca | — | | 1/11 |
| 4,222 | orchardcroft.ca | Agriculture / farming / cannabis | keyword | 1/11 |
| 4,223 | orchardgo.ca | Agriculture / farming / cannabis | keyword | 1/11 |
| 4,224 | orionchineserestaurant.ca | Food / restaurant / beverage | geo | 1/11 |
| 4,225 | orsolyakiss.ca | — | brandable | 1/11 |
| 4,226 | osecours.ca | Education / training / coaching | keyword | 1/11 |
| 4,227 | osteou.ca | Healthcare / medical / mental health | brandable | 1/11 |
| 4,228 | otb-training.ca | Education / training / coaching | keyword | 1/11 |
| 4,229 | oteas.ca | Food / restaurant / beverage | brandable | 1/11 |
| 4,230 | ottawadiamondflooring.ca | General services (cleaning, plumbing, contractors) | geo | 1/11 |
| 4,231 | ourcrazyadventure.ca | Travel / tourism / hospitality | niche | 1/11 |
| 4,232 | ourimmigrantstory.ca | Education / training / coaching | niche | 1/11 |
| 4,233 | owensoundartbanner.ca | — | | 1/11 |
| 4,234 | ownershiplifecycle.ca | — | keyword | 1/11 |
| 4,235 | ownstr.ca | — | niche | 1/11 |
| 4,236 | pacificmembers.ca | Finance / banking / insurance | keyword | 1/11 |
| 4,237 | packagedesigns.ca | Retail / e-commerce / shop | keyword | 1/11 |
| 4,238 | pamelabarnett.ca | — | keyword | 1/11 |
| 4,239 | panaply.ca | — | brandable | 1/11 |
| 4,240 | pancakeshack.ca | Food / restaurant / beverage | keyword | 1/11 |
| 4,241 | pantherdisplay.ca | Retail / e-commerce / shop | keyword | 1/11 |
| 4,242 | paquetterealestategroup.ca | Real estate / housing / mortgage | geo | 1/11 |
| 4,243 | paradigm-seb.ca | — | niche | 1/11 |
| 4,244 | paradisenh.ca | — | niche | 1/11 |
| 4,245 | paramnahal.ca | — | keyword | 1/11 |
| 4,246 | parisabeauty.ca | Beauty / cosmetics / salon | keyword | 1/11 |
| 4,247 | parksidepets.ca | Pets / animals / vet | keyword | 1/11 |
| 4,248 | parmaidentity.ca | — | keyword | 1/11 |
| 4,249 | parteeonthego.ca | Food / restaurant / beverage | | 1/11 |
| 4,250 | partyfacemusic.ca | Entertainment / media / arts | niche | 1/11 |