Multiplayer has been added to Just Cause 3 on PC today, thanks to a group of modders known as Nanos.
The multiplayer mod, called JC3:MP, allows hundreds of players to populate one server and take part in racing, deathmatch, free roam, and other game types cooperatively or competitively. You can download the mod launcher at the group’s website.
The mod had been in development for a year before releasing it in beta last month. The stable release today only requires users to be signed into Steam and running a copy of Just Cause 3. The group notes in the FAQ that a Steam release may happen with future versions.
Developers of the original multiplayer mod for Just Cause 2 announced back in 2015 that they were working on a follow-up for Just Cause 3. The mod was cancelled last summer after the lead developer on the project was hired by Avalanche Studios, developers of the Just Cause franchise.