Wearing a stunning sequinned playsuit with T-bar sandals, Kelly glittered as she arrived at Steam And Rye - which she co-owns - a venue refurbished to look like New York's Grand Central Station.
With her famous brunette locks hanging loose, Kelly arrived at the recently-opened bar and restaurant with a big smile on her face - confident in the knowledge she looked absolutely gorgeous.
Still believed to be single after splitting from rugby player Danny Cipriani earlier this year, Kelly partied with friends including former EastEnders star Preeya Kalidas until the early hours.
Well-wishers on Twitter included actress Helen Flanagan, who said "happy birthday beautiful" while Kelly thanked her, replying: "Thank you darling and thank you for being a great friend."
Made In Chelsea star Ashley James joked: "You share a birthday with @MileyCyrus - better do a birthday twerrrk."
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