Arnold Schwarzenegger's Son Christopher Hits Gym, Shows Incredible We -

Arnold Schwarzenegger's son, Christopher, is in the middle of an impressive transformation ... looking super fit as he steps for a workout.

25-year-old Christopher hit up a gym Tuesday in L.A., and while it wasn't his dad's iconic spot -- Gold's Gym in Venice -- it's clear he's been putting in the kinda fitness work for which his dad became famous. Just check the muscles poppin' outta Christopher's sleeves!

Christopher started his weight loss journey back in 2020 ... and while he tends to keep a lower public profile than the rest of his fam, it's easy to see how much more fit he's gotten over the last 3 years.

Arnold congratulated Christopher on his exercise regimen on his 24th birthday, writing, "Between your boxing classes, your weightlifting classes, your stretching classes, your cycling classes, and on and on, I can’t even keep up with you!"

BTW, he and his brothers -- Patrick and Joseph -- have all been working hard on their physique, walking in pops' footsteps.

Gallery Launch Gallery Arnold's Flexing Photos Launch Gallery Getty

Of course, those are some big shoes to fill -- no one's saying they're heading for Mr. Olympia -- but Arnold's influence on all their fitness goals is clear!