12:14 PM -- LeBron James was clearly watching every second of the first-round matchup ... 'cause the Lakers superstar was quick to congratulate his former coach on the 71-67 upset win over BYU.

"YEAAAAHHHH @DruOnDemand LFG!!!! Go Dukes @DuqMBB," Bron said on Thursday.

As the saying goes ... it's gotta be the shoes!!

The Duquesne basketball team got a sweet surprise before their first-round game in the NCAA Tournament ... brand new LeBron James XXI kicks -- from the King himself!

The Lakers superstar had the white and light blue sneakers delivered to the 11th-seeded team this week before Thursday's game against 6th-seeded BYU ... in the tourney's East Region.

The players were HYPED when they saw the new shoes ... and were super appreciative of the gift.

FYI, the LeBron 21s "Blue Diver" dropped this month ... with Air Zoom cushioning and a glow-in-the-dark outsole. The shoe was modeled after an Oyster shell.

There's a deeper meaning ... and it's a tribute to Bron's daughter, Zhuri, and how the proud dad protects his daughter just as a shell shelters a pearl.

You're probably asking, why Duquesne? Well, James' former high school basketball coach is their current HC ... Keith Dambrot, who has been the coach of the Dukes since 2017.

The special delivery comes on the heels of Duquesne's biggest basketball game in decades ... they haven't been in the NCAA tourney in 47 years, and last made a trip to the Final 4 in 1940, 84 years ago.