The 29-year-old from Los Angeles has not fought since she was pummelled to an upset defeat by Holly Holm in 2015.
Following the loss, Rousey went into seclusion and kept a low profile in the build up to the Nunes fight by declining to do interviews.
“I am very focussed and I know how I am going to stop her. I can’t wait,” Nunes, of Brazil, told the Los Angeles Times.
The Holm loss also shattered the mystique that Rousey had developed during the 12 straight wins that kick-started her career.
Saturday’s (Dec 31) UFC women’s contest will be just the 14th of her career while Nunes has fought 17 times, including four losses.
Rousey, a former Olympic judo medallist, is one of MMA’s biggest stars who has helped widen the sport’s global appeal.
So it is no surprise that her return after a protracted absence has created a huge buzz with organisers predicting record pay per view buys.
She was battered by Holm when the two met in Melbourne in November 2015 in what is seen as the biggest upset in women’s MMA history.
Rousey’s rise through the ranks of MMA earned her comparisons to Mike Tyson’s emergence in boxing’s heavyweight division during the 1980s, with the fighter generating excitement after a string of whirlwind knockouts.
However, unlike Tyson, who had fought 37 times before suffering his first loss, Rousey had fought just a dozen times as her boxing inexperience was woefully apparent when she was beaten by Holm.