Amari Cooper is one of the best route runners in the NFL … and now the Dallas Cowboys star has a chain to prove it, copping an incredible diamond piece worth $300k!!!

The 27-year-old wideout recently created a new Instagram page that focuses on his fascinating route running ability … called, you guessed it, “The Route Runner.”

To celebrate the launch, AC hit up Gabriel The Jeweler — go-to guy for some of the biggest sports stars in the world — for a truly incredible chain.

We’re told the pendant has 170 carats of VVS diamonds … and the chain is just one of four Gabriel’s ever done!

Put that all together, and the piece is valued at around $300k!!!

But, don’t worry, Cooper is doing pretty well financially — he is in the middle of a 5-year, $100 million deal.

As we previously reported, Cooper’s gone to Gabriel in the past … including an epic Cowboys jersey chain, as well as a piece repping his hometown!!!

As for the season, he had 13 receptions for 139 yards and 2 touchdowns against the Super Bowl champion Tampa Bay Buccaneers in Week 1 … so yeah, not too shabby.