The Countryfile presenter and ex-Strictly Come Dancing star, 40, will front Blue Planet II Live In Concert in 2019.
She said she was “honoured” to have landed the role.
“The TV series was such a fantastic and enlightening show and has really empowered society to view our oceans and environment with a great deal more care,” Rani said.
“I can’t wait to stand on stage with an 80-piece orchestra and huge screen showing some of that incredible Blue Planet II footage. It should be an amazing experience.”
The event will feature the original immersive TV music score, performed live by the City of Prague Philharmonic Orchestra.
Visuals from the landmark BBC One series will be projected on to a giant LED screen.
Blue Planet II, which showed the impact plastics are having on the oceans and marine life and fuelled debate on Government policy and the future of the planet, was the most watched TV show of 2017 in the UK, reaching more than 37 million viewers.
Organisers said that all the arena venues in the tour aim to reduce the use of plastic, lower carbon footprints, reduce energy consumption and improve awareness.
The BBC recently announced a Blue Planet II follow-up, featuring Liz Bonnin, Chris Packham and Steve Backshall.
The 13-date UK and Ireland arena tour takes place in March.
Information can be found at www.blueplanet2live.co.uk