Serena Williams has tipped Madison Keys to succeed her as world number one after a 7-6 (7/5), 6-3 Italian Open victory that handed the 21-time Grand Slam champion her first title of the season.
It was the first all-American WTA claycourt final since Williams beat her older sister Venus to win her maiden French Open title in 2002.
But in the end, Williams' power and experience made the difference as she claimed her first title of the year, her 13th on clay and 70th overall.
Williams becomes just the fifth woman to achieve such a total in singles after Martina Navratilova, Chris Evert, Steffi Graf and Margaret Court.
"It feel greats to win a title, especially on clay," said Williams, who will now prepare for the defence of her French Open title at Roland Garros.
Having lost two finals this season, Williams' win comes in timely fashion before Paris: "It was important to go out there and win one (title)."
It was a week of shocks in the women's draw, with a number of seeds falling before getting to the business end of the tournament.
Keys, 21, is one of several emerging women's players from the US and had wowed the Rome crowd in a battling semi-final against Spanish third seed Garbine Muguruza.
She had conceded defeat to Williams on two previous occasions, at the last two Grand Slam events, the US and Australian Opens.
On Sunday, Keys started with conviction, breaking Williams in the opening game and taking the first set to a tiebreak.
But despite occasionally stunning Williams with a ferocious return of serve and dominating on winners - 17 to 13 - Keys paid for unforced errors.
Keys, who had eight more unforced errors than Williams, admitted just being in the final with her compatriot had left her feeling nervous.
"No matter how many times you play Serena, you always go in and you can just feel her presence," said Keys.
"That's always an extra thing that you have to be worried about during the match. But for me today it really wasn't so much about how big the tournament was or anything like that.
"It was really just wanting to go out and do my best and give my best performance."
Despite conceding defeat, she was given a strong vote of confidence by Williams.
"I think Madison's a great player, I really do. Always have. I think she's got potential to be number one in the world," she added.
"It's always great to hear that from her," said Keys. "She's obviously an amazing champion, and she's won so many matches and tournaments.
"Hearing that is definitely something that makes me just work harder."
Williams pulled out injured from last year's event when Russia's Maria Sharapova triumphed.
In Sharapova's absence, due to an ongoing doping ban, Williams claimed her 13th title on clay, the most of any active player on the WTA Tour, to add to her previous wins from Rome in 2002, 2013 and 2014.