Mr Schwarzenegger posted a video of the charge on Twitter and Instagram:
I'm absolutely in awe of these beautiful animals, and I wish people would stop killing them for their ivory. pic.twitter.com/FYtO94aXU6? Arnold (@Schwarzenegger) May 31, 2016
And also wrote:
I couldn't have written this encounter better if it was for a movie. Some of us had to change our pants. Take a photo, not a shot.? Arnold (@Schwarzenegger) May 31, 2016
The 68-year-old former California governor and bodybuilder was in South Africa for an annual fitness conference and exhibition named after him.
The short video clip shows a large elephant menacing the open game viewing vehicle, as Mr Schwarzenegger is heard saying: "He's going to charge us."
The elephant does charge and the vehicle moves sharply off with the elephant running behind.
Mr Schwarzenegger did not reveal which game park he was visiting when the video was shot - nor who it was who had to "change (their) pants."
More than 30,000 African elephants are killed by poachers every year to supply an illegal trade controlled by criminal gangs feeding demand in the Far East.