Swiatek clinched the ranking after defeating Viktorija Golubic 6-2 6-0 in the second round of the Miami Open, becoming the first Polish player to ascend to the No 1 position in singles.
She will become the new world No 1 when the WTA rankings are released on April 4
At 20 years, 308 days old, Swiatek will be the youngest player to make her No 1 debut since Caroline Wozniacki in 2010.
"It's a dream come true, for sure," Swiatek said. "It's that kind of thing that I wanted to happen someday, but I didn't really know that it's going to be possible for me.