The Hollywood beauty prompted speculation about her love life when she flashed a new band beneath her diamond engagement ring on the red carpet at the Academy Awards and again as she presented the Best Actor prize to The Artist's Jean Dujardin.
Ballet choreographer Millepied was also photographed wearing a simple silver ring on his left hand.
Representatives for the famously-private couple have declined to comment on the reports, but now former ballet dancer-turned-jewellery designer Jamie Wolf has revealed the rumours are true.
She tells Usmagazine.com, "I designed the rings worn by Benjamin Millepied and Natalie Portman. They were made with recycled platinum and conflict-free diamonds."
Details about when and where the couple exchanged vows have yet to surface.
Picking Wolf to create the wedding rings was an easy choice for the stars - she danced with Millepied at the New York City Ballet and befriended Portman on the set of Black Swan, in which she played a dancer.
She is also the same jeweller the Frenchman approached to create Portman's engagement ring.