I'm underage. Can I book a hotel room in Canada?

I doubt vey much if any hotel will let a room to a 15 year old. Try the YMCA.

People under the age of majority (18 or 19 depending on province) are not responsible for contracts they enter into. Therefore, businesses are not required to deal with minors. Renting a room is a consumer contract. And hotels do all they can to protect themselves from people staying and running off or trashing the room, etc. If they rent to a 15 year old, it would be their fault, so they don't.

Next problem, for the same reason credit card companies don't give minors credit cards and it is very difficult to get a hotel without a credit card. If allowed, they require a large deposit upfront.

Most hotels won't rent rooms to teenagers at all. It's not so much a legislated law, just company policy for most places.

If you find a hotel that will rent a room to you at 16, I guarantee you it won't be the kind of place you want to stay at. It'll be the sort of place that rents rooms by the hour to hookers and drug dealers, and they most likely won't have a reservation website.

If I were you, I would not want to spend 3 days alone in Toronto. Too many people who are looking for young international visitors hang out in that city.

While there is no actual law, in fact, very, very few hotels would rent to someone under 18. And, those that did are places no young person should ever be in. You can legally move out in Canada (and Ontario) at 16, so, it is legally possible then, but, still pretty unlikely.

you have to contact the hotel might be able to do it if parents book,toronto is a big place be careful there.

A hostel might. Hotels do not.