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.
Swiatek who won her maiden Grand Slam title at the French Open in 2020 and has already won titles in Doha and Indian Wells this year.
Photo: PHOTOSPORT Caption Poland's Iga Swiatek