The 32-year-old and rapper Meek, 27, only went public with their relationship this month, but rumours have been circulating about them since the beginning of the year.
Taking to Twitter to tease fans with the news, Nicki posted emojis of a ring, a heart and a diamond and added ‘I’ll post it later’.
And she didn’t disappoint, following up with a picture of her massive yellow diamond.
The heart-shaped rock is surrounded by dozens of tiny white diamonds, and a jeweller has confirmed it would have cost in the region of $500k [£337k].
A Nicki insider told E! News: “Both Meek and Nicki have been spending amazing quality time together lately and have gotten extremely close these past few months.
“It may seem like it all is happening very quickly but Nicki and Meek are in this 100 per cent. They truly love each other.”
Meek, real name Robert Rahmeek Williams, has yet to comment on the news.
It comes after Nicki ended her relationship with long-term boyfriend Safaree Samuels last year.
Congratulations to Nicki and Meek!