Hayley Matthews, the West Indies allrounder and T20 World Cup winner, has signed for Welsh Fire, while Colin de Grandhomme will continue his stint at the Ageas Bowl after replacing Andre Russell on Southern Brave's list of overseas players.
Matthews, who was Player of the Match when West Indies won the 2016 World T20 in Kolkata, was unveiled by Welsh Fire after it was confirmed that Suné Luus has returned a positive Covid-19 test and is not able to travel.
Meanwhile de Grandhomme, who made a career-best 174 not out for Hampshire on his LV= Insurance County Championship debut, and was part of the New Zealand squad that claimed the World Test Championship mace against India last month, takes over from Russell who has been ruled out due to international commitments and Guyana's status on the UK red list.
Marchant de Lange will start the competition for Trent Rockets after Wahab Riaz's arrival was delayed by visa issues, while the New Zealander Glenn Phillips will now play the entirety of the tournament for Welsh Fire in place of Kieron Pollard, who has pulled out due to injury.
Adelaide Strikers batter Katie Mack has been signed by Birmingham Phoenix as a replacement for Ellyse Perry who has withdrawn from the competition due to personal reasons. Amy Jones will now captain the side.
It has also been confirmed that Ollie Pope will miss the start of the Hundred as he recovers from a quad injury, while Alice Monaghan replaces Hannah Jones at London Spirit.
"When I got the call to join Southern Brave it was an easy decision," de Grandhomme said. "I've settled in really well at Hampshire and I'm hoping to create some more fantastic memories at the Ageas Bowl. I'm really looking forward to linking up with Devon Conway again and all of the guys can't wait to get going."
Hayley Matthews added: "I'm thrilled to be taking part in The Hundred this summer. It'll be a lot of fun to play in Cardiff alongside the like of Sarah Taylor in front of big crowds. The Hundred can help move women's cricket forward and it'll be great to take part."
Beth Barrett-Wild, Head of The Hundred Women's Competition said: "I'm gutted for Suné Luus, I know how excited she was about playing for Welsh Fire in The Hundred this summer, but we all wish her a very speedy recovery. In Hayley Matthews we have a big stage player, in brilliant form, coming in, and I'm sure she will be looking forward to the opportunity to show off her skills."