Chad Johnson -- My 10-Year-Old Daughter's a World Class Sprinter!

Speed runs in Chad Johnson's family -- and the proof is in his 10-year-old daughter ... who's one of the fastest little girls in the country ... TMZ Sports has learned.

We've spoken with a bunch of important people in the track and field world who tell us there's buzz around Cha'iel Johnson (aka "Moca") ... who posted a BLAZING 29.5 in the 200 meters in 2014.

She's only gotten faster since then and has been smoking people in major competitions across the country ... while speed training with her famous father.

In fact, Moca is set to compete in the 200m, 400m and 800m sprints at the National Junior Olympic Track and Field Championships in Jacksonville later this month ... and Chad says he couldn't be more proud.

Johnson says he LOVES his daddy/daughter time -- and now that he's not in the NFL, he's had a lot more time to be a hands-on parent.

But Chad says it's important to keep Moca humble -- which is why he also races her full speed ... and dominates ... saying, "I want her to know there's room for improvement. But she's quick as hell."