The Hundred is the England and Wales Cricket Board's (ECB) new short-format cricket tournament, consisting of eight brand-new teams competing concurrently in men's and women's competitions.
Mack was called into the squad as a replacement for Ellyse Perry, who withdrew due to personal reasons.
Mack will join fellow Australian and former Meteors teammate Erin Burns at the Phoenix as one of only three overseas players in the squad.
The Meteors opening batter enjoyed a stand-out season in 2020/21, scoring 418-runs across the WNCL season to finish with the second highest tally in the competition. Mack also brought up her 1500th run for the Meteors in the opening round of the season and rounded out the year playing her 50th match for the blue and gold.
To cap of a stellar summer, Mack also took home her third Bronwyn Calver Medal for Meteors Player of the Year at the recent ACT Cricket Awards.
The Hundred officially kicks off on July 21, with the Birmingham Phoenix first game to be at home against the London Spirit on July 24.