Meet Mary Slack: SA’s richest woman and Harry Oppenheimer’s daughter
Mary Slack is a South African businesswoman, philanthropist, and leading figure in horse breeding. She is the eldest daughter of the late mining tycoon Harry Oppenheimer and his wife Bridget McCall Oppenheimer, and is widely regarded as South Africa’s richest woman.
Source: UGC
TABLE OF CONTENTS
Key takeaways
- Mary Slack previously worked at Oppenheimer Memorial Trust and Market Theatre.
- She owns the Wilgerbosdrift stud farm in Piketberg, Western Cape.
- Mary is one of the largest donors to the Democratic Alliance and contributed significantly to the Solidarity Fund during the COVID-19 pandemic.
- She has also supported theatres, ballet, and arts initiatives across South Africa for decades.
Mary Slack’s profile summary
| Full name | Mary Slack |
| Date of birth | December 1943 |
| Age | 81 years old (as of 2025) |
| Place of birth | Johannesburg, South Africa |
| Current residence | Brenthurst Estate, Parktown, Johannesburg |
| Nationality | South African |
| Ethnicity | South African |
| Hair colour | Blonde |
| Eye colour | Blue |
| Father | Harry Oppenheimer |
| Mother | Bridget McCall Oppenheimer |
| Siblings | Nicky Oppenheimer |
| Marital status | Divorced |
| Ex-husband | Gordon Waddell, Henry Richmond Slack |
| Children | 4 |
| School | Heathfield School, Ascot |
| University | Sorbonne University |
| Profession | Businesswoman, philanthropist, thoroughbred horse breeder |
Mary Slack hails from South Africa
The popular businesswoman was born and raised in Johannesburg, South Africa. Her parents are Harry Frederick Oppenheimer and Bridget McCall. Her father was of German-Jewish and Czech-Jewish descent.
Harry Oppenheimer was a well-known South African businessman, industrialist, and philanthropist. For about 40 years, he was regarded as the country’s leading industrialist and was often listed among the richest people worldwide.
In 2004, he was ranked 60th on SABC3’s list of Great South Africans. Harry died on 19 August 2000.
Source: Original
Her brother is a billionaire
Mary Slack grew up with her younger brother, Nicholas F. Oppenheimer, a billionaire businessman. As of 2025, Nick is the third-richest person in Africa, with an estimated net worth of $12.7 billion, according to the Bloomberg Billionaires Index.
He previously served as chairman of the De Beers diamond mining company and its subsidiary, the Diamond Trading Company, and was also the deputy chairman of Anglo-American.
Source: Getty Images
She attended Sorbonne University
The South African philanthropist attended Heathfield School in Ascot, Berkshire, England, where she held the position of head girl. She later furthered her studies at Sorbonne University in Paris.
Mary Slack’s career journey
Mary began her professional career when she co-founded Wiphold, an investment company that made history as one of the first women-led firms on the Johannesburg Stock Exchange. She also owned Amaridian, an art gallery in New York’s SoHo district.
Leadership roles
In 1971, Mary became a trustee of the Oppenheimer Memorial Trust, a charitable foundation created by her father, and later became its chairwoman. She also served as the managing trustee of Johannesburg’s Market Theatre from 1989 to 1992.
Source: Getty Images
In 1997, Mary started Business and Arts South Africa and became its first chairwoman. She has also led the Brenthurst Library and Brenthurst Press, supported the Mzansi Ballet, and helped raise money for Dorkay House, a historic arts venue.
Horse racing and breeding
Growing up in a horse-loving family, Mary began focusing on horse breeding in the early 1990s. In 1997, she opened her Wilgerbosdrift stud farm in Piketberg. After her mother passed away in 2013, her daughter Jessica took over the family’s Mauritzfontein stud farm, and the two farms were combined, now owning around 150 mares.
Mary’s horses have won major races, such as Sparkling Water winning the 2022 Durban July and Claymore winning at Royal Ascot the same year. She also became one of the first non-resident members of the Hong Kong Jockey Club.
Philanthropy and politics
Source: Getty Images
Mary is a major philanthropist. She donated R1 billion to South Africa’s Solidarity Fund during the COVID-19 pandemic. Mary has also funded music projects, such as an album by Allen Kwela, and supported the creation of the African Leadership Academy.
She is also a significant donor to political parties, especially the Democratic Alliance (DA), where she was one of the largest individual backers before the 2024 general election.
Mary Slack’s net worth: How rich is Harry Oppenheimer's daughter?
As of 2025, Mary Slack’s net worth is closely tied to the Oppenheimer family’s immense fortune, which is estimated at around $10.4 billion according to Forbes. She manages more than $3 billion in assets.
Who is Mary Slack’s husband?
As of 2025, Mary Slack is not married, but has been married twice before. She was first married to Gordon Waddell, a Scottish rugby player, whom she met in 1962 and married in 1965. The couple divorced in 1971, and Waddell won custody of their two daughters, Victoria and Rebecca.
Source: UGC
As per Peerage, Mary was also married to Henry Richmond Slack, and together they had a daughter, Jessica Slack-Jell. However, it is unclear when the couple married and when they separated, as the details of their relationship have not been made public.
Mary Oppenheimer’s daughters, Victoria Freudenheim, Rebecca Diamond, and Jessica Slack-Jell, are recognised as significant political donors, particularly supporting the Democratic Alliance and other political groups in South Africa.
Frequently asked questions
- How old is Mary Slack? As of 2025, Mary Slack is 81 years old, having been born in December 1943.
- How many children does Mary Slack have? The popular entrepreneur has four daughters, including Victoria Freudenheim, Rebecca Diamond and Jessica Slack-Jell.
- What does the Oppenheimer family own in South Africa? The Oppenheimer family has businesses in mining, farming, wildlife conservation, and other areas, including big shares in De Beers and Anglo-American.
Conclusion
Mary Slack, the eldest daughter of Harry Oppenheimer, has built her business career beyond her family’s mining legacy. She is a successful businesswoman, philanthropist, and horse breeder. She currently resides at the Brenthurst Estate in Johannesburg and is the mother of four daughters, some of whom are well-known political donors.
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Source: Briefly News
