All three Tests between South Africa and the British and Irish Lions will now be staged in Cape Town as a result of the Covid-19 pandemic.
The series was scheduled to head to Johannesburg for the second and third Tests after starting in Cape Town.
However, the decision to remain in Cape Town was made following "extensive consultation" with medical experts.
Jurie Roux, chief executive of SA Rugby, said the data "pointed in only one direction".
"The series has already been significantly disrupted by Covid-19," added Roux.
"We now have two teams in bio-secure environments without any positive cases or anyone in isolation. To now return to the Highveld would expose the series to renewed risk.
"Everyone wants to see the two squads, at their strongest, play out an unforgettable series over the next three weekends and this decision gives us the best opportunity to see that happen."
The Lions' managing director Ben Calveley said the touring party were "fully supportive" of the decision, which is in "the best interest of the Test series".
The Lions played their opening two games of the tour in Johannesburg before facing the Sharks in Pretoria then moving to Cape Town.
The Test series will be played at the Cape Town Stadium at the same time (17:00 BST) on three successive Saturdays from 24 July to 7 August.
British and Irish Lions 2021 XV
Pick your starting XV for the first Lions Test on 24 July 2021.
Phone: (800) 737. 6040
Fax: (800) 825 5558
Website: 
Email: 
