The pair will each head a team of three players, including two professionals, at the prestigious event at Birmingham's NEC on April 19.
"I've played polo before and really enjoyed it so I'm definitely looking forward to going head-to-head with another celebrity and hopefully scoring a few goals!" said Price.
Guy, who stars as Siren on the Sky1 endurance show, told Horse And Hound that she is "really excited" about competing.
"My Gladiators training keeps me very fit but I will be having a few polo lessons to get me prepared. It sounds like a brilliant show and I hope to see some of my fans there to cheer me on!" she said.
Tickets for the event are available to buy now.