The Olympic athlete will discuss winning her gold medal in the Heptathlon, as well as her upcoming wedding to fiancé Andy.
ITV bosses are said to be "delighted" to have secured Ennis for the first show, which will also feature Colin Farrell, Kelly Brook and Rita Ora.
"Jessica is the woman of the moment. To have her confirmed for the show's comeback next Saturday night is fantastic," a source told The Sun.
"Despite her huge success, she is very down-to-earth and humble. Viewers will lover her."
Justin Bieber and Liam Neeson will appear on The Jonathan Ross Show later in the series.
It was recently reported that producers of Strictly Come Dancing, I'm a Celebrity... Get Me Out of Here and Dancing on Ice are battling to sign Olympic medallists from Team GB.
Photo gallery - London 2012 Olympics:
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