O’Donnell, 23, is back in red after previously representing the Renegades in WBBL|03 and the Hobart Hurricanes in WBBL|04.
The Mildura product won the 2020-21 Una Paisley Medal after scoring 488 runs and claiming 25 wickets for Melbourne CC, returning to the Victorian squad in the process.
“I’m pumped to be back with the Renegades. I’ve got some really good mates here and I’m excited to be part of this group,” O’Donnell said.
“I fell back in love with the game last year, have enjoyed being part of a professional environment again this year and am looking forward to testing myself in an elite competition.”
Gardner has earned her first professional contract at the age of 16.
The left-arm pace bowler plays at Dandenong CC, alongside Renegades’ skipper Sophie Molineux, and has rapidly risen through the Victorian underage pathway.
“I’m super stoked – I can’t wait to get around the girls, it’s going to be such a good experience for me,” Gardner said.
“I’ve already played some games with Sophie and I was over the moon when I found out that I was joining the Renegades. Hopefully I can get some game-time, take some wickets and be part of a winning team.”
O’Donnell and Gardner will travel to Tasmania this week with the Renegades’ Victorian-based players.
“Rhiann returns to the Renegades on the back of a fantastic Premier cricket season last year,” WBBL Head Coach, Simon Helmot, said.
“With her all-round abilities and previous WBBL experience, we believe she can add to our group in a variety of roles this season.
“Poppy is an exciting, young cricketer and this is a great opportunity for her.
“She is just 16 years old but has shown plenty of promise in Premier cricket and will only continue to grow and develop her game as part of this squad.”
The Victorian duo finalises the Renegades’ local player signings for the season.
“Rhiann and Poppy are both great additions to our squad and we’re delighted to have them onboard,” General Manager, James Rosengarten, said.
“These signings lock in our local playing contingent for WBBL|07. We’ve also got some exciting international player signings to announce shortly, as we keep building towards the start of the season.”