The 31-year-old blonde bombshell sizzled in a cerulean minidress, which showed off her slim limbs and tiny waist.
Rachel Riley's eye-popping outfit also featured a racy cut-out in the back and elbow-length sleeves as the maths whizz elongated her pins further with a pair of towering black stilettos.
With a tight-fitting top and flaring out in a skater-style skirt, today's ensemble left little to the imagination as the material stretched over her assets.
Rachel Riley flashed the flesh in a very short dress on Countdown today
Rachel sizzled in the skimpy number Rachel Riley in pictures Fri, March 3, 2017
Rachel Riley is the Carol Vorderman of the naughties. She co-hosts Countdown and here are some of her best pictures
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Rachel Riley steals the show in baby blue dress
Her golden locks fell loose in their usual straight style around her shoulders as she dutifully presided over the letters board on the Channel 4 gameshow.
The Countdown favourite sparked pregnancy rumours earlier today when she shared a snap of herself with cradling her "baby bump" alongside her friend and make-up artist Lauren.
Fans needn't worry that Rachel will be leaving her job on the show, however, as her bump, unlike Lauren's was actually fake.
The former Strictly Come Dancing star tucked a hot water bottle up her dress as she imitated her friend's blossoming bump, wishing her well by saying: "Can't believe it's the best makeup artist in the world's last days already!
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Her ensemble featured a racy cut-out in the back
Rachel sparked pregnancy rumours with a funny Instagram snap earlier today
"Good excuse though Lauren, I hope yours is as easy to remove as my hot water bottle bump," she added. "Bring baby Zlatan in as soon as he or she arrives, we're gonna miss you!"
Rachel regularly delights viewers of the long-running gameshow with her titillating style choices, and last week she flaunted her famous figure in a skintight purple number as she took her usual position on the Countdown podium.
She set pulses racing in the tight-fitting number, which clung to her curves, making her peachy posterior impossible to miss.
Countdown airs weekdays at 2.10pm on Channel 4.