Boulter, who is set to play at the Nottingham Open this week, will take up the mantle for the first time in her career despite being beaten by Yanina Wickmayer in the final four.
"Naturally, I am very proud to join the women before me who have reached that historic spot," she said.
"However, my main goal remains on improving my ranking and continuing to work hard.
"It's going to be an exciting summer as we are all very close in the rankings."
Boulter is now ranked 126th in the world, two ahead of Raducanu and in front of fellow Brits Jodie Burrage (131), Katie Swan (134) and Harriet Dart (143).
The Leicestershire-born player's achievement comes at the expense of Raducanu, who soared to the top spot after her dramatic victory at the US Open in 2021.
She has since found success difficult to replicate having been hampered by injuries, contributing to a drop to a world ranking of 128.
Raducanu is currently idle on the WTA Tour after undergoing hand and ankle surgery, which kept her out of the French Open and will ensure she is absent from Wimbledon.
