A contentious statement if there ever was one. But as far as officially recognised brands go, the Bass Brewery logo is the first. It was registered on 1 January 1876 by a Bass Breweries employee who queued overnight on new years eve of 1875 (According to wikipedia at least. It’s probably not true, but it makes for a good story). Yes I know it’s not really the first brand, even Bass Breweries was founded almost a century before in 1777, but it’s one of the first officially recognised.
Funny how little has changed in over 140 years, it could be on a beer bottle today. The greedy bastards at Bass Breweries have also got the second ever trademark, for different versions of their famed ale.