The Rock Gives Daughter KATSEYE-Themed Birthday Party With 'Gnarly' Cake!

They could describe The Rock's party-planning skills with one single word ... 'cause he threw his daughter a KATSEYE-themed bash for her 8th birthday -- and it was "gnarly!!!"

The wrestling legend and actor pulled out all the stops for Tia's big moment ... putting together a homemade cake featuring the pop group's songs and imagery -- even a sandwich from their hit music video.

If the cake wasn't enough, they put up a big banner with the group's picture on it!!

The girls were busy performing in the desert at Coachella, so they weren't available to sing "happy birthday" in person ... but Tia was clearly thrilled with the effort her pops put into her day.

"8 summers old and our anchor of pure love, joy, crazy humor 🤪 and always down to put in the work, and step outta the box! We love U baby girl," The Rock said ... adding a "Pinky’s Up ❤️‍🔥💪🏾" -- leading us to believe his daughter's had KATSEYE's new single on repeat over the past few weeks.