Arnold Schwarzenegger's Love Child -- I'M HUUUUUUUGE

If there was any doubt Arnold Schwarzenegger shtuped his former maid .... DOUBT NO MORE ... 'cause his love child is about to turn 16 -- and he looks just like his humungous father.

Standing roughly 8'2" and weighing an estimated 475 lbs (pure muscle) ... genetic jackpot winner Joseph Baena strolled alongside his mother Mildred during a shopping excursion in Bakersfield, CA yesterday.

Joseph was sporting a shirt from a swimming and diving competition -- it's unclear if he participated, but we're guessing if he did, he dominated ... based purely on his enormous physique.

Fun Fact -- Arnold first began competitive bodybuilding around the age of 16 ... and eventually excelled in competitive adultery.