Quinton de Kock has already taken over as limited overs captain.
Quinton de Kock was named captain of South Africa for the T20I series in India and has continued in that role while taking over as ODI captain as well against England at home recently. Du Plessis is expected to keep his place in the squad to play three T20s against Australia, starting at the Wanderers on Friday.
Du Plessis was also the Test captain of the Proteas, but with their next Test assignment is only in July against the West Indies, there is no hurry to find his successor.
"The last few weeks of rest away from the game have given me a lot of perspective on the great privilege and honor I have had in representing and leading my country in the three formats of this wonderful game. It has been a rewarding, sometimes tough and other times a lonely road, but I would not replace the experience for anything, because it has made me the man that I am proud to be today,” Du Plessis said.
He further added. "When I took over the leadership, I did so with the commitment to lead, perform and most importantly, to serve. As the team heads into a new direction with new leaders and a young crop of players, I feel it will be in the best interests of South African cricket to relinquish the captaincy in all formats. This was one of the toughest decisions to make, but I remain fully committed to supporting Quinton, Mark and my teammates as we continue to rebuild and re-align as a group."
Du Plessis stressed he's available for selection in all three formats. "South African cricket has entered a new era. New leadership, new faces, new challenges, and new strategies. I remain committed to playing in all three formats of the game for now as a player and will offer my knowledge and time to the new leaders of the team," he said.
Du Plessis ended his statement saying,” In a perfect world, I would have loved to lead the team in the Tests for the rest of the season as well as the T20 WC, but sometimes the most important attribute of a leader is to be selfless. I am healthy, fit, energized and motivated and certainly see myself playing an important role in the squad for as long as I continue putting in winning performances for the team."