alt Hacker News> IP addresses also are assigned by registrars (ARIN in the US and Canada, for instance).
To be pedantic for a moment, ARIN etc. are registries.
The registrar is your ISP, cloud provider etc.
You can get a PI (Provider Independent) allocation for yourself, usually with the assistance of a sponsoring registrar. Which is a nice compromise way of cutting out the middleman without becoming a registrar yourself.
You can also become a registrar yourself - at least, RIPE allows it. However, fees are significantly higher and it's not clear why you'd want to, unless you were actually providing ISP services to customers (in which case it's mandatory - you're not allowed to use a PI allocation for that)