The 31-year-old blonde bombshell kept it classy in a pretty blue frock as she performed her usual letters and numbers duties on the Channel 4 gameshow this afternoon.
Her outfit choice featured a deep blue lining and turquoise overlay, with see-through panels giving a racy glimpse at her décolletage.
The sleeveless A-line number emphasised her trim curves, cinching in at her tiny waist and flaring out over her hips.
Rachel Riley flashes a glimpse of her slender pins in a semi-sheer frock
Rachel put her figure on display in the chic A-line 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
Rachel Riley's famous pins were also on display, with the half-sheer skirt falling to below her knees.
The brainy beauty kept her golden locks in their signature straight bob, looking fresh-faced with a touch of rosy pink blush across the apples of her cheeks and co-ordinating nude pink lipstick.
One viewer took to Twitter to compliment her ensemble, gushing: "Always covet the dresses that @RachelRileyRR wears on @C4Countdown."
The blue number featured racy sheer panels around her waist and décolettage
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Rachel flaunted her peachy posterior in a skintight number last week
Rachel regularly titillates Countdown fans with her fashion choices as many tune in to see what style treats she has in store each day.
Last week, the Channel 4 favourite poured her curves into a skintight purple dress, drawing plenty of attention to her peachy derriere.
Countdown airs weekdays at 2.10pm on Channel 4.