Nick Kyrgios and Grigor Dimitrov will meet in the Cincinnati Open men's final while Garbine Muguruza will face Simona Halep in the women's final.
Australian Kyrgios beat David Ferrer 7-6 (7-3) 7-6 (7-4) while Bulgaria's Dimitrov advanced against John Isner 7-6 (7-4) 7-6 (12-10).
Spain's Muguruza eased past top seed Karolina Pliskova 6-3 6-2, while Halep beat Sloane Stephens 6-2 6-1.
Romanian Halep will become world number one if she wins the tournament.
"I think it's something special to get number one in the world," said Halep, who would move above Czech Pliskova.
"Everyone can get to number one now. The ranking is close. I really want that."
Kyrgios happy to 'scrap out the win'
In the men's final, Kyrgios will be chasing his first title of the year after a hard-fought victory over stubborn Spaniard Ferrer.
"He was a nightmare to play, especially because I'm a tall guy and he's not the tallest guy," said Kyrgios, who beat world number two Rafael Nadal in the quarter-finals.
"In the tie-breaks I served well, but I definitely didn't bring my best tennis.
"I'm just really proud that I managed to scrap out the win."
Dimitrov saved a set point in the second set tie-break against American Isner before reaching his first Masters 1000 final.
"It's a good step," said Dimitrov. "I have been on the tour for quite some time now, and I appreciate those moments.
"I'm starting to appreciate them even more."
Murray and Soares through to doubles final
In the men's doubles, Britain's Jamie Murray and Brazilian partner Bruno Soares continued their flawless run as they eased past second seeds Lukasz Kubot of Poland and Brazil's Marcelo Melo 6-4 7-5 to reach the final.
The pair have not dropped a set at this year's competition and will face France's Pierre-Hugues Herbert and Nicolas Mahut - who also won their semi-final in straight sets.