The 'Arthur' actor was seen smooching with the BAFTA-winning actress - famous for her roles in 'Two Pints of Lager and a Packet of Crisps', 'Gavin & Stacey' and 'Benidorm' - after his 'A Night of Spontaneous Comedy' show at London's Soho Theatre Comedy bar on Tuesday night (21.05.13).
Sheridan had been in the audience at the show, and has also been spotted hanging out with Russell at a food festival last week, but denies any romantic link with the notorious lothario.
On the night of his show, she wrote on Twitter: ''Just had dinner with lovely friends. And yes they're wrong yet again. He's one of my best mates Xx (sic).''
After the Soho Theatre Sheridan - dressed in a black dress and brown heels - was escorted to a nearby hotel by Russell's driver, where she continued the evening in the bar. The comedian-and-actor - who was divorced from singer Katy Perry last year - followed her a short time later.
Sheridan - who last had a short relationship with film director Reg Traviss - claimed last month she has never been on a date, saying: ''I've just filmed a drama called 'Dates' but I don't think I've ever actually been on one
''I haven't really been swept off my feet. I haven't been asked out, or maybe I would go. Then again, the idea of sitting opposite someone and making chit-chat - that makes me cringe!
''Everyone is obsessed with linking me up but I'm alright at the moment!''
Despite them kissing, Sheridan denies she and Russell are dating.