Kath Fox (also Kath Shaughnessy) is a fictional character from the BBC medical drama Holby City, played by actress Jan Pearson. She first appeared in the series two episode "Knife Edge", broadcast on 23 December 1999. Kath arrives at Holby City hospital as a Ward Sister. She is characterised as a devout Catholic with high moral values and the over-protective mother of Danny Shaughnessy (Jeremy Edwards). Writers played off her strong faith, often making it centric to various dramatic plots they conjured up for her. Over a four-year period she became a tortured character who had been domestically abused by her husband Simon Shaughnessy (Andrew Dunn). The stigma of a divorce in her religion makes her feel unable to leave him.

She befriends and later falls in love with a priest, Father Michael (Martin Ledwith). Following a near fatal beating from Simon she moved on to a romance with moneyed Terry Fox (Miles Anderson), but their happiness is short-lived because of Terry's terminal cancer. Writers featured her in a euthanasia story, when she agrees to assist him in committing suicide. A feud with her step-daughter Lisa Fox (Luisa Bradshaw-White) was created and Kath found herself standing trial for assisted suicide. Kath was then a regular feature in a controversial serial killer plot, in which patients are murdered by staff nurse Kelly Yorke (Rachel Leskovac). She tries to frame Kath, who lays blame to Kelly's brother Nic Yorke (Liam Garrigan), which results in Kelly stabbing Kath in a near fatal clash.

Following the succession of bleak stories for her character, Pearson decided to leave Holby City. She had made her intentions clear to producers in 2003 and they convinced her to stay for an extra year. The actress requested her unlucky character leave the show amidst a happy ending. Writers introduced Larry Phillips (Dominic Mafham) as Kath's love interest and they move away together. Pearson has stated that Kath became one of the show's best loved characters. Critics of the genre have praised her portrayal of Kath, though Jim Shelley from the Daily Mirror criticised Kath, whom he believed often went against her own faith and morals.

Kath was a respected and excellent Ward Sister. She was resolute in the face of anything life threw at her. She had a calm nature which made people warm to her. A devout Catholic, she had her faith tested many times. After a number of traumas, she left Holby for pastures new with Architect Larry.

— An excerpt from Kath's profile on the official Holby City website.

The character first appeared in the series two episode "Knife Edge", which was broadcast on 23 December 1999. Kath is characterised as a "devout Catholic" and her strong faith causes her issues with a series of relationships writers created for her. She has an "easy-going and calm nature" which makes her well liked with colleagues and patients. Her Catholicism is referenced in the show. She uses her beliefs to help other characters, such as those who question their faith. Pearson described her character as "rather saintly by nature". She is a "very protective" mother to Danny Shaughnessy (Jeremy Edwards), but her attitude towards him constantly leaves him embarrassed. Kath struggled to come to terms with Danny growing up and becoming independent. She interferes in his work life and he becomes irritated with her. Following an "emotional confrontation" he decides to move out. When Danny leaves home Kath begins to suffer from 'empty nest' syndrome and seeks solace through her working life. Throughout her tenure writers have maintained a troubled personal life for Kath, through various doomed romances and dramatic storylines. Pearson has also described her on-screen counterpart as having "a hard life".

Pearson found challenging to play a character as "resolutely nice" as Kath is. She said that she is completely different to more "edgy" roles she has played previously. While Pearson states she is completely unlike Kath, she uses her own experiences to play her. She was once a teacher at a Sunday school and used this when portraying Kath's religious aspects.

One of Kath's early issue lead stories was becoming the victim of domestic abuse from her husband Simon Shaughnessy (Andrew Dunn). Initially Kath develops feelings for her colleague, the consultant general surgeon Mike Barratt (Clive Mantle). When they attend a course together they almost share a kiss. This tests Kath's faith and she decides to distance herself from him. Kath briefly break up with Simon, but he convinces her to return with the promise of counselling sessions. Simon tries to change his ways but his aggression towards Kath heightens the following month. She then bonds with a patient named Linda (Sonia Beinroth) whose husband has attacked her. Simon had long been aggressive towards Kath but it was only when she was admitted to the hospital following a "severe beating", would her colleagues discover the abuse. It happens after she becomes close with the on-site priest Father Michael (Martin Ledwith), which makes Simon jealous. When Father Michael drops Kath off at home following a church service, Simon beats Kath up and she is rushed into the hospital for emergency surgery. Danny becomes desperate to protect Kath from his father. He and Father Michael secure and decorate a new flat for Kath to live in when she is discharged. Father Michael gives Kath the courage to leave Simon for good. But their relationship cannot progress because both of their commitments to religion. Father Michael offers to leave the church but Kath believes it is wrong and ends their relationship.