Kouga Municipality Mayor Elza van Lingen died, at the age of 68, on Thursday morning after a nine-year battle with breast cancer.
She was surrounded by family and loved ones at her home in Cape St Francis, the municipality said in a statement.
Kouga Speaker Horatio Hendricks, who has been acting mayor since Monday, said her death had come as a shock and that councillors and municipal staff were in mourning.
"We knew she had cancer, but she was fighting it all the way. Just last week, she was in Kou-kamma, moving from voting station to voting station for the by-election that took place there."
He said she had an incredible work ethic.
"Even when she went for chemotherapy, she never took the day off, but would first come to the office or return to her duties directly afterwards.
"She was a mentor to many of us and was very active on the ground. One of her favourite sayings was that a good leader’s shoes should never be clean."
DA federal chairperson Athol Trollip said Van Lingen had been a great friend and formidable leader, who worked hard for the residents of Kouga.
"Our thoughts and prayers are with Elza’s family at this difficult time. Elza was a kind and generous person who has left a lasting impact on all those she met, worked with and served."
Van Lingen was born in Willowmore in the Eastern Cape.
Became councillor in 2002
She and her husband, Michael, ran a merino stud farm, and farmed livestock and game. She had apparently been invited before to get involved in politics, but had declined as her four children were still young.
"That changed once her four children were grown up. The couple moved to Cape St Francis in 2000, where they ran a guesthouse," said the municipality.
"The quality of the water in the town was of great concern to Van Lingen and her efforts to rectify it earned her an invitation to join the Cape St Francis Civic Association. Their main focus was on service delivery and the environment."
She joined the DA in 2002 and was elected as a councillor.
After serving as a councillor for around six years, she was elected by the DA to serve in the National Council of Provinces during the 2009 Elections.
In November 2011, she was elected as DA leader in the NCOP and reelected in 2014.
She was also elected leader of the Tsitsi-Kouga constituency, which included Kouga, Koukamma and Baviaans.
Van Lingen became mayor after the DA’s 2016 victory in Kouga.
A memorial service will be held for her at 14:00 on Monday at Mentors Country Estate in Jeffreys Bay.