She opted for a curve-hugging, high-necked red jumpsuit with loose trousers, leaving fans gawping as she did the numbers.
The skintight ensemble left little to the imagination as Rachel showed off her award-winning derriere.
Viewers rushed to social media to compliment Rachel on her choice of outfit, as one fan posted: “This outfit really shows Rachel’s figure off.”
Another added: “Jesus Rachel you’re amazing.”
A third wrote: “She is such a queen.”
A fourth wrote: “Rachel Riley is so damn hot.”
The presenter also left her fans drooling after she uploaded a series of raunchy holiday snaps.
Rachel could be seen in a tiny bikini as she posed in front of a stunning backdrop, and another picture showed her in a plunging kaftan dress.
Her snaps were from a summery getaway to the Maldives with her Strictly dancer boyfriend Kovalev.
The pair have been together for four years after meeting on the BBC show back in 2013.
Countdown continues tomorrow at 2.10pm on Channel 4.