No one. This currency isn’t physically printed in the shadows by a central bank, unaccountable to the population, and making its own rules. Those banks can simply produce more money to cover the national debt, thus devaluing their currency.
Instead, bitcoin is created digitally, by a community of people that anyone can join. Bitcoins are ‘mined’, using computing power in a distributed network.
This network also processes transactions made with the virtual currency, effectively making bitcoin its own payment network.