South Africa 191 for 5 (Hendricks 70, Markram 51*, Willey 3-25) beat England 101 (Bairstow 27, Shamsi 5-24) by 90 runs
Southampton: A dismal batting display saw a pitiful England suffer a heavy 90-run defeat in the deciding Twenty20 against South Africa to lose the series 2-1.
Chasing 192 to win, they were blunt with the bat, going 55 balls without hitting a boundary at one stage, before being dismissed for 101 in 16.4 overs.
It is the fourth time in six T20s this summer that England have been bowled out and there was another failure for Jason Roy, who made 17 off 18 balls.
Jonny Bairstow top-scored with 27, while South Africa's left-arm wrist spinner Tabraiz Shamsi ripped through England with career-best figures of 5-24.
Defeat means England have lost a third successive T20 series, after defeats by West Indies and India this year, for the first time and they have failed to win a white-ball series in a home summer for the first time since 2013.
Reeza Hendricks had earlier made 70 off 50 balls and Aiden Markram hit an unbeaten 51 off 36 as the Proteas brilliantly paced their innings to post 191-5.
The returning David Willey was the pick of England's bowlers, taking 3-25, including removing Quinton de Kock in a wicket maiden at the start of the innings.
England are next in action when a three-Test series against South Africa starts at Lord's on 17 August.
Their next T20 assignment will come in a seven-game tour of Pakistan in late September before three T20s against Australia leading into this year's T20 World Cup in October and November.