The Greek Freak finished with 41 points and 13 rebounds.
Following a tense first quarter, Milwaukee exploded in the second to take a 15-point lead into half-time.
The Bucks only built on their advantage from there, with Antetokounmpo seemingly unstoppable down the stretch as he finished with 41 points and 13 rebounds.
Chris Paul led the way for Phoenix with 19 points but Devin Booker was far from his best, posting just 10 points on 3-14 shooting.
Milwaukee will look to even the series at 2-2 when game four gets underway on Wednesday (Thursday morning UK time).