John, 27, damaged her calf during a training session as the squad prepares for the new World Rugby global tournament in October.
The 35-times capped international had recently returned to training after a shoulder injury ruled her out of the final two games of Wales’ 2023 Six Nations campaign.
John, an experienced campaigner and leader in the Wales squad will miss the whole tournament and her return to play and rehabilitation programme will be supervised by the Welsh Rugby Union.
John said: “This is really heartbreaking after working so hard to get back to fitness and seeing how hard the squad is working ahead of the fantastic and exciting challenge of the WXV in New Zealand.
“These are the tournaments we all want to play in and missing the opportunity with the squad to test ourselves against the best sides in the world is a real blow for me on a personal level after setting my sights on making the squad.
“I will support the squad from Wales but my focus now is on doing my rehab and getting back to full fitness ahead of the next Six Nations.”
