Top seed Nadal, 31, profited from a timely rain delay at a break when he was down in the final set to hold off defending champion and No. 2 seed Alexander Zverev 6-1, 1-6, 6-3 in Rome.

Nadal surrendered top spot in the ATP world rankings to Roger Federer last week after Nadal's Madrid Open quarterfinal defeat to Dominic Thiem -- the only blight on an otherwise impeccable clay-court season this year.

However, Nadal will return to the summit when the latest ATP rankings are published Monday after the Spaniard overcame world No. 3 Zverev in a thrilling finale on the Foro Italico's Campo Centrale.

Billed as a clash between the two current top-form players on clay, Sunday's final did not disappoint. After two hotly-contested semifinals on Saturday -- Nadal saw off long-time rival Novak Djokovic while Zverev smashed a racket in anger during his victory over Marin Cilic -- the championship match ebbed and flowed throughout.

Despite dropping serve in the opening game, victory looked like a foregone conclusion for 10-time French Open champion Nadal as he blistered through the first set in 33 minutes to put his young opponent on the back foot.

However, Zverev produced a phenomenal set of tennis to force the decider. The German changed tactics in the second set, becoming much more aggressive on the front foot and overwhelming Nadal with an array of powerful strokes.

The 21-year-old secured a double-break to move 5-0 ahead. After Nadal prevented the bagel, he leveled the match in style with a ferocious backhand winner down the line.

Rising star Zverev's confidence grew further as he immediately broke Nadal at the start of the third, before the match's turning point came in agonizing fashion.

With Zverev leading 3-1 in the final set, rain intervened and caused an hour's delay in play. It proved pivotal, allowing Nadal precious time to regain his composure and hit back immediately after the restart.

Nadal rattled off four consecutive games -- including two successive breaks of serve -- to move 5-3 ahead before serving out a fifth to secure his eighth Italian crown and send out a warning to his rivals ahead of the year's second grand slam.