Branden Grace withdrew from the Olympics on Friday, becoming the fourth golfer to cite the Zika virus as a reason not to play in Rio de Janeiro this summer.
At No. 11 in the world, Grace, a two-time winner this year, is the highest-ranked South African golfer.
"After serious consideration, it is with regret that I have decided to withdraw myself from the Olympic competition due to the risk posed by the Zika virus," Grace said in a statement. "Although it was a huge goal of mine to represent my country in the Olympics, we are getting married in November and hoping to start a family in the near future, so I must put the health of my family first."
Brazil has been the hardest hit of the approximately 60 countries that have reported an outbreak of Zika, the mosquito-borne virus linked to severe birth defects and possible neurological problems in adults.
The announcement comes two days after Rory McIlroy of Northern Ireland, the No. 4 player with worldwide appeal among golf's growing list of young stars, said he won't be part of golf's return to the Olympics because of Zika. McIlroy also is engaged and said he plans to start a family soon.
Former Masters champion Charl Schwartzel said three weeks ago that Zika was behind his decision to withdraw. Schwartzel said he and his wife plan to have more children and that he would play if he were single or if the Olympics were held elsewhere.
Marc Leishman of Australia also cited Zika because his wife's immune system has not fully recovered from nearly dying last year of toxic shock syndrome.
Others who withdrew — Adam Scott of Australia, Louis Oosthuizen of South Africa, Vijay Singh of Fiji and Graeme McDowell of Northern Ireland — did not specifically cite Zika. McDowell, who was next in line to replace McIlroy, said his wife is expecting their second child about two weeks after the Olympics and he had no plans to be out of the country in the weeks leading up to the birth.
Golf is returning to the Olympics for the first time since 1904. It already is set for the Tokyo Games in 2020, though the IOC will vote next year to determine whether the sport should be a permanent addition to the program.
Still to be determined is whether Jason Day, the No. 1 player in the world, decides to play.
Day began to hedge three weeks ago when he mentioned his wife wanted more children and said he was wary about going and needed to make a smart choice. Earlier this week at a preview day for the PGA Championship, he said he respected McIlroy's decision.
"It's a tough one going from trying to represent your country and trying to win a gold medal, but also understanding that it's a life decision that you have to make," he said.
Grace's decision is a blow to South Africa because its best three players — Grace at No. 11, Oosthuizen at No. 14 and Schwartzel at No. 23 — all have pulled out. Next in line would be Jaco Van Zyl and Brandon Stone, who won the South African Open at the start of the year but has yet to play in a major.
Grace said he wishes the South African teams well and apologized to fans for withdrawing.
"It would have been a huge honour to represent my country, so I really hope to be able to qualify again in four years' time," he said.