His flamboyant caning of his native South Africa for 149 not out means England go into the fourth day today with ambitions extending beyond the draw that previously looked their limit.
England closed on 351 for 5, 68 behind South Africa's first-innings total and hoping a miserable weather forecast proves wrong, while South African morale was not boosted by the sight of skipper Graeme Smith limping off injured towards the close.
Pietersen passed a series of statistical landmarks, overtaking the career aggregates of local hero Len Hutton (6971 runs), his own captain Andrew Strauss (6994) and Sir Donald Bradman (6996), before nudging the single off spinner Imran Tahir that made him the eighth England batsman to get 7000 runs in Test cricket.
But far more significant than that – or the fact that 15 runs later he recorded his 21st Test century, one behind the England record jointly held by Walter Hammond, Colin Cowdrey and Geoff Boycott – was the mood change he accomplished.
England had been on the back foot since the series began. The slaughter at The Oval was followed by clear, if not decisive, South African dominance over the first two-and-two-thirds days here.
When Ian Bell, lunging at a ball from Jacques Kallis, was caught just before tea at first slip by Smith, there were pessimistic mutterings that England, at 173 for 4, might not reach the follow-on target of 210.
Pietersen, accompanied by debutant James Taylor, went in for the interval on 43 not out. The decisive expansiveness of his movements from the start suggested he was in the mood for something spectacular.
He was at his best against South Africa's star paceman Dale Steyn, who fuelled the flames by greeting him at the wicket with a head-high bouncer. Steyn is No 1 in the world rankings and looked it against England's other batsmen, taking two wickets for 28 runs in 72 deliveries to them.
He bowled 72 balls to Pietersen – and was treated with profound disrespect. Pietersen struck him for 64 runs, starting with the vehement pull to the boundary that opened his score and culminating with contemptuous treatment of the new ball. A sumptuous pull through mid-wicket was followed by a giant six.
The post-tea barrage that brought Pietersen 106 runs in three hours and ten minutes was signalled by a surge of 26 runs, including six fours, in 11 deliveries. It also included a let-off, as Oval hero Hashim Amla dropped him at short leg off Steyn's opening partner Morne Morkel,
His second 50 came at very nearly a run a ball, watched from the other end by the diminutive Taylor, whose competence and composure suggested that England's two-season search for a number six to succeed Paul Collingwood might be at an end.
Taylor scored only 34 out of 147 runs in a fifth-wicket partnership but batted with a mature control that was an unspoken rebuke to England's fallible top order, before being bowled by Morkel.
Matt Prior struck a sparkily combative 20 not out before the close of play at half past seven.
Earlier in the day England had lost Alastair Cook lbw to Vernon Philander for 24, Strauss caught behind for 37 off Steyn, the strangely skittish Jonathan Trott to a slip catch off Steyn for 35 and Bell, dismissed the same way off Kallis, for 11. The steady fall of wickets and a sluggish scoring rate meant South Africa kept the ascendancy established at The Oval. But then came Pietersen.