Mulder's mammoth effort went past the 311 not out that Hashim Amla scored against England at the Oval in 2012, the Proteas' only other individual triple centurion in the longest format.
Mulder's innings was the sixth highest individual score in Test history while the all-rounder became the 29th Test cricketer to strike a triple hundred.
It was also the second fastest 300 recorded in Test cricket, coming off 297 deliveries - beaten only by India's Virendar Sehwag's 278-ball effort against the Proteas in Chennai in 2008.
In what is his first match as captain of the Proteas, Mulder also beat Graeme Smith's mark of 277 as the highest score by a South African skipper in a Test match.
With Brian Lara's world record of 400 in his sights, Mulder decided to declare his team's innings at lunch on the second day at the Queen's Sports Club.
Highest individual scores in Test cricket
400* - Brian Lara for West Indies v England, Antigua 2004
380 - Matthew Hayden for Australia v Zimbabwe, Perth 2003
375 - Brian Lara for West Indies v England, Antigua 1994
374 - Mahela Jayawardene for Sri Lanka v South Africa, Colombo 2006
367* - Wiaan Mulder for South Africa v Zimbabwe, Bulawayo 2025
Wiaan Mulder produced a captaincy debut for the ages on Saturday, scoring a record-breaking unbeaten 264 to put South Africa in a dominant position on Day One of the second Test against Zimbabwe.
Lesego Senokwane and Prenelan Subrayen will both make their Test debuts as the Proteas made three changes for the second and final Test against Zimbabwe that starts in Bulawayo on Sunday.
Corbin Bosch admits he has not yet come to grips with matching the feat of legendary Proteas all-rounder Jacques Kallis in the first Test victory against Zimbabwe in Bulawayo.
Proteas stand-in captain Keshav Maharaj has been ruled out of the second Test against Zimbabwe due to a left groin strain with Wiaan Mulder set to take over the leadership reins.
