Trace is the official rival name in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!
In every core Pokémon RPG series, there's always a rival character who takes part in the story to spur you throughout the campaign—and Let's Go is no exception.
Pokémon rivals have mostly been nameless over the years to give players a chance to name them after a hated enemy, a good friend, or their real-life rival. Some people, however, like to play the game from the perspective of the game's lore and would prefer to use a rival's official name.
So what's the rival officially called in the Let's Go games, you ask? In short, the character is called Trace.
There you have it folks, go ahead and call your rival Trace when you load into your next playthrough. Or don't—it's your call, after all.