This is the updated version of The Pirate Repulic mod originally made by lpslucasps.

I've decided to fork his repo and maintain the mod since he has been inactive for the last 16 months. Contributions are welcome and encouraged.

Here is his description of the mod:

This mod adds some flavor to pirates. It's easy to completely ignore them, specially in the late game, when they are no more than a nuisance. They are pretty inconsequential.

Now, if a system with pirates stays unnatended for too long (10 years or more), the pirates will try to seize a nearby colony. If they win, they will become an independent megacorp with the Criminal Heritage civic!

There's more: the newly-formed "Pirate Republic" may offer to become your tributary in exchange of the system. This offer will only appear if you do not already have another rebelious pirate as a vassal.

This mod was inspired by this suggestion published on the official Stellaris forums.