The Ontario government debt is the net amount of money the Government of Ontario has borrowed from the general public, institutional investors and public-sector bodies. As of March 31, 2018, the Ontario government's total debt is projected to be CDN $348.79 billion. The Debt-to-GDP ratio for 2017-2018 is 37.1 % and interest on the debt is CDN $11.97 billion, representing 8.0 % of Ontario's revenue and its fourth-largest spending area.

Who does the ontario government borrow money from? Let's have some stream of consciousness first.
To answer the question, consider the following: The Ontario government debt is the net amount of money the Government of Ontario has borrowed from the general public, institutional investors and public-sector bodies. So, the answer is the general public.