Not a brand new format but pretty new. Not an official format but gaining traction by each tournament. Recently there was the European Championship in Finland a week or two ago.
Format identity: Magic as it was before Modern. The sets from 4th Edition and to Scourge are legal.

This means no rotation. No new cards ever.
I have only played it a little bit but it seems very fun. It is actually possible to play a control deck with no creatures. Oath of Druids has no insane targets. Squee, Goblin Nabob is a cool value engine.
Link to official website:
https://premodernmagic.com/blog/category/ban-list/
Format identity: Magic as it was before Modern. The sets from 4th Edition and to Scourge are legal.

This means no rotation. No new cards ever.
I have only played it a little bit but it seems very fun. It is actually possible to play a control deck with no creatures. Oath of Druids has no insane targets. Squee, Goblin Nabob is a cool value engine.
Link to official website:
https://premodernmagic.com/blog/category/ban-list/