Previously, the record for the Transvaal-born but well-travelled artist was the £490,000 hammer seen for Congolese Woman from 1946 which sold at Christie's in London in December 2007.
But this figure was smashed first by Strauss & Co (10% buyer's premium) in Cape Town on October 11 when the colourful still life from 1939 Gladioli took R12m (£1.18m), and then by Bonhams (20/12% buyer's premium) who took £2.1m for Bahora Girl on October 27.
Painted in 1945, the latter, an arresting image of a beautiful Indian woman from Irma Stern's time in Zanzibar, had been acquired directly from the artist by a member of the vendor's family.
The 2ft 10in x 2ft 4in (87 x 71) oil on canvas came in its original Zanzibar frame and was estimated at £600,000-900,000.
It sold to a buyer in the room, who saw off multiple telephone bidders.
Contrary to some reports, this was not a record for a South African artist. That accolade belongs to Marlene Dumas (b.1953) whose 1995 painting The Visitor made £2.8m at Sotheby's in July 2008.
By Alex Capon