And, he's praising the "UFC 1" champion for paving the way for everyone else!

"Royce Gracie is the one that really changed the sport," GSP tells TMZ Sports ... "[He] changed the entire belief system of what a real fight is."

Gracie is a LEGEND -- who famously won 3 FIGHTS IN A ROW IN THE SAME NIGHT at UFC 1 back in 1993.

The UFC events back then were tournament-style -- where winners advanced to another fight in the same night.

Oh, and weight classes weren't a thing back then either! So you had giant dudes fighting small dudes with basically no real rules.

Gracie went on to win UFC 2, UFC 4 and fought to a draw with Ken Shamrock in the championship fight at UFC 5.

Royce also popularized Gracie Jiu-Jitsu (Brazilian Jiu-Jitsu) -- which revolutionized the sport.

"We should never forget the guys that were there before us," GSP says ... "We should never forget about these guys. Like Einstein says, we stand on shoulders of giants. They've paved the way for us."

Gracie was inducted into the UFC Hall of Fame in 2003.

Georges says Jon Jones is the best modern-era fighter -- but argues Khabib Nurmagomedov should be in the conversation as well.

Watch the video -- it's great.

There's more ... GSP also tells TMZ Sports about his new fitness program on TV.fit -- a "well-being application" that helps people get and stay healthy!

"There's programs for everybody or people that are older, yoga. There's also a book on mental health, there's a lot of things. It's a lot more than a fitness app and there's nothing like it on the market right now."