Quebec shares a land border with four northeast states of the United States (Maine, New Hampshire, New York and Vermont) and with three other Canadian provinces (New Brunswick, Ontario and Newfoundland and Labrador). However, as said in the Etymology and boundary changes section, a border dispute remains regarding the ownership of Labrador. The border with Labrador is still not officially recognized by the Quebec Government. A maritime boundary also exists with the territories of Nunavut, Prince Edward Island and Nova Scotia. Quebec has officially more than 12,000 kilometres (7,500 mi) of borders of all types. Half of these are land limits, 12% river limits and 38% marine limits.

is there a border between ontario and quebec?
yes