Here's the best Rookie of the Year trophy ever ... Quavo hooked up NBA star Trae Young with a custom diamond chain for his huge 1st season in the league -- and the bling is awesome!!!
"Welcome to the A," the rap star told Young as he presented the jewelry.
Trae killed it for the Atlanta Hawks this year ... averaging 19.1 points and 8.1 assists per game in 81 starts -- and to show his thanks, Migos' Atlanta superfan got him some ice.
The chain -- made by famous ATL jeweler Wafi -- is pretty epic .