The Oscar-winning actor was photographed Monday ringing in the big 5-0 down in Mexico -- Cabo, to be specific -- and like we said ... the guy was definitely ready to show off his huge guns for the cameras, 'cause he was hanging out on the balcony without a shirt on.

He was also wearing a towel around his waist at one point too ... big-time thirst trap vibes.

Eventually, CB popped on a top, hat, and shades to shield himself from the rays ... making his way down to a beach with his wife, Sibi Blažić, and their nine-year-old son Joseph. We'll say this about him ... even when clothed, Christian puts other dad bods to shame.

Christian and Sibi are also parents to daughter Emmeline, 18 ... although, she didn't appear to be on the family getaway here.

The Hollywood actor is clearly making the most of his downtime after taking a bit of a breather on the career front -- his only 2023 credit was voiceover work for "The Boy and the Heron" ... and he currently has nothing in the pipeline this year.

Granted, he's still one of the most prolific actors working today -- and he's still killing it at this point in his career. He can most certainly afford to take a break from on-camera work.

Lucky for us (and everyone else) ... he's right here putting on another type of show, no general admission tickets needed either.