Jem Costello is a fictional character from the British Channel 4 soap opera Hollyoaks, played by Helen Russell-Clark.

In December 2009, in an interview with entertainment website Digital Spy series producer Lucy Allan revealed that there would be a new female arriving in Hollyoaks who would be a threat to Steph Cunningham (Carley Stenson) and Cheryl Brady (Bronagh Waugh).

[3] In January 2010, it was announced that Lucy Allan had stepped down from the position of series producer and that Paul Marquess had taken over the role.

[4] It was soon revealed that Marquess planned to give Hollyoaks a "shake up", changing the productions team[5] and beginning a cast cull by axing three established characters.

[6] In April 2010, it was announced that Marquess would introduce a second new family after the Sharpe clan, the Costello's consisting of mother Heidi (Kim Tiddy), father Carl (Paul Opacic), sons Riley (Rob Norbury) and Seth (Miles Higson)[7] and daughter Jasmine (Victoria Atkin).

of her character, Russell-Clark stated, "Well, Jem’s well into her martial arts – as I am, which means you’ll be seeing lots of fight action.

"[3] In March 2010, in a video interview with Hollyoaks Backstage, Russell-Clark introduced her character and described her personality, she said, "Jem is a bit of a free spirit, she loves travelling, she loves anything like new experiences, big ideas, she's full of big ideas [...] She's quite feisty, she's really into her martial arts and keeping fit and stuff.

"[11] Gilly Roach (Anthony Quinlan) decides to go travelling around the world with Zoe Carpenter (Zoë Lister) and Mike Barnes (Tony Hirst) after he gives up on his love for Steph.

During her time with the family, Jem works in The Dog in the Pond and starts running a martial arts class teaching a lovestruck Duncan Button (Dean Aspen).

Jem reunites with her step-mother Heidi and brothers Riley and Seth but refuses to talk to Carl after his numerous affairs.

Jem then starts studying for her play which is graded on, helps Kevin Smith (Cameron Crighton) and Jamil Fadel (Sakinder Malik) through their problems.