Katherine will play Harriet Finch - a rival for Ashley Thomas as she wants to become the first woman vicar at St Mary's church in the village.
The actress told the Emmerdale website: "I am delighted to be joining the cast of Emmerdale. Harriet is great fun and I'm looking forward to seeing the character unfold."
Katherine played mother and teacher Sally Hunter in Hollyoaks for four years until 2005. Her other notable roles include appearances in the award-winning This is England and the first series of lottery drama The Syndicate. She has also made several one-off appearance in Coronation Street.
Harriet is a relative of village busybody Edna Birch, and arrives during a speed-dating event at The Woolpack where she and Ashley instantly clash.
She will appear on screen in Emmerdale from next month.
Patrick McLennan is a London-based journalist and documentary maker who has worked as a writer, sub-editor, digital editor and TV producer in the UK and New Zealand. His CV includes spells as a news producer at the BBC and TVNZ, as well as web editor for Time Inc UK. He has produced TV news and entertainment features on personalities as diverse as Nick Cave, Tom Hardy, Clive James, Jodie Marsh and Kevin Bacon and he co-produced and directed The Ponds, which has screened in UK cinemas, BBC Four and is currently available on Netflix.
An entertainment writer with a diverse taste in TV and film, he lists Seinfeld, The Sopranos, The Chase, The Thick of It and Detectorists among his favourite shows, but steers well clear of most sci-fi.
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