The year 2139 is the two-thousandth, one-hundredth and thirty-ninth year of the Common Era.
- October: The Pan-Asian Coalition begins invading the European Union. This begins the Cold War, a war over the resoures of the world, during an ice age (Battlefield 2142).
- November: The PAC enters Minsk led by General Arkadi Petrov. The EU's Krieg Panzer 2nd Regiment begins their defense the city, which lasts till the PAC specialforces force their withdraw four months later (Battlefield 2142).
- Unknown Date: Saren Arterius is born (Mass Effect (series)).
- Unknown Date: Kahlee Sanders is born (Mass Effect (series)).
- Unknown Date: Emory Erickson attempts to top his earlier invention, the transporter, by inventing a sub-quantum transporter. In the end it’s a failure and loses him his son, Quinn Erickson, in subspace (Star Trek: Enterprise).
- Unknown Date: Charles Tucker III joins the Earth Starfleet (Star Trek: Enterprise).