The 19-year-old Spaniard ended Daniil Medvedev's 19-match winning streak 6-3 6-2 to reclaim the top spot in the ATP rankings he lost to Novak Djokovic in January.
Medvedev – who has climbed one spot to number five – had won his three previous tournaments in Rotterdam, Doha and Dubai.
He had also won the pair's only previous meeting – at Wimbledon in 2021 – but the 27-year-old had no answer to his teenage opponent’s patient but aggressive game plan in windy conditions.
Alcaraz seized control with an immediate break in both sets, opening a 3-0 lead in the first and winning the opening 10 points in the second as he raced away to a 4-0 lead.
And he rarely looked troubled as Medvedev failed to repeat the sparkling form from his semi-final victory over Frances Tiafoe.
Alcaraz hit 18 winners to Medvedev's five, repeatedly exploiting his opponent's deep position with a string of drop shots.
He clinched his third ATP Masters 1000 title – joining compatriot Rafael Nadal as the only men to reach that mark as a teenager – without facing a break point.
And he will chase a fourth, still two shy of Nadal's tally before turning 20, when he aims to defend his Miami Open title from Saturday.
"It feels amazing to lift the trophy here, to recover the No. 1 [ranking]... I would say this has been the perfect tournament," he reflected, as per atptour.com.
"It was good for me, [at] this tournament that I really wanted to win, and for me, it's amazing.
"I have no doubts about my shots. I feel really comfortable on court. I really trust in every shot that I hit. Of course, that's why I'm playing a great level, because if I miss, I don't mind. I don't care about the miss. I'm just trying to hit 100 per cent in every shot and having no doubts about the shot."