Celebrities Oprah Winfrey and Reese Witherspoon as well as Bumble founder Whitney Wolfe Herd have invested in Spanx, the shapewear maker said, as it completed a majority stake sale valuing the company at $1.2 billion to investment firm Blackstone Inc.

Other new investors included female-founded investment funds G9 Ventures and Able Partners, Spanx said on Thursday.

"Oprah was a big reason for Spanx's early success when she named it one of her iconic 'Favorite Things' in 2000," founder Sara Blakely, who now serves as its executive chairwoman, said in a statement.

Blackstone has plans to expand Spanx globally and help it strengthen its online business. It has previously invested in Herd's online dating app Bumble and Witherspoon's Hello Sunshine media firm, among other female-led businesses.