Walter, who has held the position since March 2023, has attributed his resignation to personal reasons.
He played an instrumental role in South Africa's recent successes on the global stage. Under his leadership, the Proteas made history by reaching their first-ever ICC Men's T20 World Cup final in 2024, where they finished as runners-up to India in Barbados.
A record run of eight consecutive wins underpinned the campaign. His tenure also saw the 50-over side reach the semi-finals of the ICC Men's Cricket World Cup 2023 in India. In his time at the helm, Walter oversaw the national side in 36 One-Day Internationals and 31 T20 Internationals, with series wins against Netherlands, Australia, Ireland and Pakistan.
His final assignment was the ICC Champions Trophy 2025 in March, where he led the Proteas to another semi-final appearance, this time against New Zealand in Lahore.
"Coaching the Proteas has been an incredible honour, and I am immensely proud of what we have achieved together," said Walter. "The players, support staff, and the South African cricketing community have been fantastic throughout this journey. While it's time for me to step away, I have no doubt that the team will continue to grow and reach even greater heights."
Director of National Teams and High Performance Enoch Nkwe said: "Rob has done an immense job for South African cricket over the past two years.
"It is also important to recognise Rob's commitment to expanding the talent pool across both formats. While in charge, he ensured that emerging players had the opportunity to develop and make their mark at the highest level, which will be critical for the future of the Proteas.
"We have a busy period of white-ball cricket over the next two years as we build towards the Cricket World Cup on home soil. His successor will continue to work towards that 50-over World Cup campaign, along with next year's T20 World Cup."
CSA Chief Executive Officer Pholetsi Moseki added: "Rob played a significant role in the rebuilding of the Proteas brand on the international stage. During his two years in charge, we have witnessed a significant increase in faith in South African cricket, largely due to the team's performance.
"His professionalism and work ethic have been exemplary, and he will undoubtedly be missed. On behalf of Cricket South Africa, we wish him all the success in the future."
A successor will be announced in due course.
Temba Bavuma suffered his first defeat as Test captain after the Proteas went down by 214 runs against Australia in Durban, and the home skipper could not hide his disappointment.
Aiden Markram battled for almost six hours at the crease but a career-best bowling effort from Josh Hazlewood saw Australia complete a 214-run win against the Proteas in the first Test in Durban.
The Proteas will face a battle on the final day to save the opening Test against Australia in Durban, going to stumps on 102-4 after being set a target of 421.
Australia have earned a 139-run lead over South Africa after bowling out the lacklustre hosts for 284 runs in their first innings at Kingsmead Stadium on Sunday.
