Snooker legend Steve Davis, Westlife singer Kian Egan and EastEnders actress Laila Morse will also take part in the annual reality competition.
Emmerdale's Lucy Pargeter, designer David Emanuel, Miss GB Amy Willerton, TV host Matthew Wright and The Fresh Prince of Bel-Air star Alfonso Ribeiro complete the lineup.
Adlington said: "It's a once in a lifetime opportunity. It's a chance for me to do something completely different in my life.
"I am also looking forward to being part of a team again. Since I retired, I have missed that team environment and so I am really looking forward to feeling like a big family, enjoying working together and being part of all the banter."
Davis stated: "I'm not really using the jungle as any type of 'stepping stone' but purely just to have a laugh and a challenge."
Essex beamed: "Five years ago, I started watching the show and now I really can't believe I am going to be going in the jungle. I am so happy. I can't say this enough. What an incredible opportunity."
Ant & Dec return as hosts of the long-running series, which launches on Sunday, November 17 at 9pm.
Laura Whitmore, Joe Swash and Rob Beckett will also host I'm a Celebrity…Get Me Out Of Here Now! every night on ITV2.
I'm a Celebrity 2013: All this year's contestants: