Thousands showed up to celebrate Dwayne "The Rock" Johnson becoming a Disney Legend ... and they wound up serving as his daughter's birthday choir.

The Rock was midway through an emotional acceptance speech Sunday at D23 in Anaheim, CA, when he spotted Simone Johnson in the audience and turned his attention to their own Disney history.

The proud dad recalled taking Simone to the Mouse House when she was just 5 years old and having breakfast with the princesses ... then pointed out his eldest daughter had just turned 25.

That's when he cued the sold-out Honda Center crowd ... leading thousands of people in singing "Happy Birthday."

Simone -- a fourth-generation wrestler known professionally as Ava -- celebrated her birthday August 14. Dwayne also gave a shout-out to his younger daughters, Jasmine and Tiana, who were watching from home.

The Rock was inducted by his "Jungle Cruise" costar Emily Blunt ... joining a 2026 Disney Legends class that included Anne Hathaway, the Jonas Brothers, Lin-Manuel Miranda and Bob Iger.

The Rock accepted the award ... then handed the spotlight to Simone.