Williams beat Maria Sharapova 6-1, 6-4 in the final of the Madrid Open Sunday to retain her No. 1 ranking and collect her 50th career title, while Rafael Nadal saw off Stanislas Wawrinka 6-2, 6-4 for his fifth title since returning from a knee injury.
The second-ranked Sharapova would have taken the top ranking with a win, but Williams stormed to an early lead as Sharapova struggled with her serve.
Despite Sharapova briefly recovering her poise in the second set, Williams' form never dipped as she defended her title.
"It feels good," Williams said of winning her 50th title. "I don't know how many more I can win. Who knows if I will ever win another title? I just want to live the dream. Hopefully, I can keep it going.
"When you first start out everything is so exciting. Now I expect to win."
Williams improved her record against Sharapova to 13-2, with her only two losses coming in 2004.
The 31-year-old Williams, playing in her first red clay final since 2002, dominated Sharapova from the start as the Russian never managed to steady her erratic serve.
"I started the match really slow and against an opponent like her you can't give her that," said Sharapova, who had won her previous seven red-clay finals. "I wasn't reacting well. I wasn't moving well. Not only the double faults I made, I didn't have a lot of great first serves in. She was really stepping up."
Sharapova committed five double faults in her first three service games, dropping the first two as Williams eased to a one-set lead. Her shaky serve let Williams gear up and land several winning shots before closing out the first set with a floating return that clipped the line.
Sharapova earned and converted her first break point to begin the second set, opening up a 3-1 advantage.
But the former No. 1-ranked player's serve again betrayed her as she hit another double fault, and Williams' precise groundstrokes set up three break points to hit right back.
Williams closed out the final after Sharapova recorded her eighth and final double fault before sending the ball long to give up her fifth service game.
Last year, Williams won here on the experimental blue clay surface that was removed after complaints from players that it was too slick.
Williams said the move back to red clay meant the tournament was a good warm-up for the French Open starting at the end of the month.
"This court is definitely different," she said. "It plays like Roland Garros and that is a plus. So I think it is great preparation."
Cheered on by the home crowd at the Caja Magica, the fifth-ranked Nadal cruised to his 55th career title and extended his head-to-head record with Wawrinka to 9-0.
Nadal flopped on his back and screamed in joy when his Swiss opponent's final volley fell long to end the match.
It was Nadal's seventh straight final since coming back from a nagging case of tendinitis in his left knee that sidelined him for seven months.
"I'm very happy and maybe this victory is even more special considering how complicated this year has been," said Nadal. "This tournament couldn't have gone better for me.
"I think this was my best match of the tournament. This was perhaps the match where I was the most aggressive."
Nadal imposed his ground game from the start. He worked his opponent around the court and punished him with passing shots when he tried to come forward.
The local favourite set the tone in the first game by breaking Wawrinka with a vicious flick to land the ball on the sideline.
Nadal, who had won here in 2005 and 2010, roared out to a 4-0 lead in 20 minutes.
The 15th-ranked Wawrinka settled down in the second set and was able to take Nadal's service game to deuce. But Nadal returned two line-drive shots by Wawrinka at the net before he fired the third try long. Nadal then drove in an ace to end Wawrinka's challenge.
"Nadal showed again that he is the best on clay," said Wawrinka, who also congratulated Nadal's coaching staff for helping him back from his layoff.
"Since he has come back he has shown that it is really tough to beat him."