Bairstow harassed the Proteas bowlers throughout his 53-ball attack as England amassed 234-6, their second-highest T20 total, continuing his impressive Test form.
In a raucous fourth-wicket partnership that lasted only 37 balls and included Moeen Ali, who hammered 52 from 18 balls, Bairstow added 106 runs, with one over going for 33 runs.
Moeen’s 16-ball fifty was the quickest by an England player, and England smashed 20 sixes, the most ever in a T20 match.
In a fielding display on the verge of becoming ridiculous, the South African team dropped Bairstow four times due to the pair’s suffering.
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The visitors had a chance to complete what would have been their record chase despite losing both Quinton de Kock and Rilee Rossouw in the second over because of 21-year-old Tristan Stubbs’ incredible 72 from 28 balls.
However, Chris Jordan bowled a composed 18th over, and Stubbs was caught at far off by Richard Gleeson’s delivery with 51 required from the last two.
South Africa finished on 193-8 after the Lancashire seamer claimed two further wickets in the over.
On Thursday, Cardiff hosts the second T20 of the three-game series as both teams prepare for the T20 World Cup in the fall.
