Photos of the piece started circulating on social media this week ... a large tattoo located on the back of the 5x NBA All-Star, next to other tats paying homage to his hometown, St. Louis.

The tattoo is taken straight from real life ... after the C's beat the Dallas Mavericks in the NBA Finals in June, securing the title.

Tatum, naturally, was one of the driving forces behind the Celtics title run, averaging 25 points and nearly 10 rebounds a game during the playoffs. During the series-clinching 5th game, Tatum had 31 points, 11 assists, and eight rebounds.

"Oh my God," Tatum said of his first title. "It's a surreal really. We did it!" Tatum said after securing his first NBA title, and the 18th for the Boston Celtics.

"We have a resilient group. We've been through a lot as a team over the last couple of years. What they gon' say now?!"

Overall, it's been a good year for Tatum. He won his first ring, signed a 5-year extension worth $315 million, and had his second kid with longtime girlfriend, R&B singer Ella Mai.