Sean Davison was sentenced in 2019 to eight years under house arrest, five of which were suspended.
"I certainly do not regret what I did," Davison told AFP.
"I helped three men suffering unbearably with no hope of recovery, who were determined to die and they were incapable of ending their own lives".
He staged a press conference to mark his release on the steps of the Cape Town High Court on Monday.
The conditions of his house arrest meant he was allowed to go to work and church, but imposed a three-year media ban.
The biotechnology professor, was arrested in September 2018 and charged with murder over three "right-to-die" cases, including of his friend, a quadriplegic man and a man with motor-neuron disease.
Davison, 59, who founded right-to-die charity Dignity SA, paid tribute to the late Archbishop Desmond Tutu for his support to the assisted dying movement campaign.
In 2016, South Africa's Supreme Court of Appeal overturned a ruling that granted a man the right to medically-assisted death and could have opened the way to legalize euthanasia.
"While I've been on house arrest, a number of countries changed the law," said Davison, citing Australia, Spain and the United States. "There is a general move around the world for a law change. And my issue has highlighted it again in South Africa, and hopefully, the politicians are going to sit up and listen and also feel the mood of the country."
South African Euthanasia Promoter Freed
FILE: In this file photo taken May 19, 2022, syringes used for injection are depicted. Many end of life decisions are made with injectable drugs causing a fatal overdose.
A South African campaigner for the legalization of euthanasia, convicted of premeditated murders of three people he helped to die, was released from house arrest Monday after serving a three-year sentence.
CAPE TOWN —