a monopoly patent was literally a government invention. an actual monopoly does require the government. what you are talking about is called a “natural monopoly” in the literature. that would be a situation where there’s only one seller for something like say water in a desert town. in that case you can have price gouging and such.

now, the important bit is the LEGAL ability to prevent competition. if there is a natural monopoly on water, and the seller decided to start charging obscene amounts for water, those extreme profits would normally induce other sellers to enter the market. **except when they are legally prohibited **, we can expect that a natural monopoly will not last if what we call “monopoly rents” are extracted.

so you see, a true monopoly requires legal force, eg the state.