Home team seal four-Test series 3-1 with 177-run victory after off-spinner takes five wickets to add to his second-innings knock of 75.
Moeen Ali 'in good rhythm' after spinning South Africa out as England clinch Old Trafford Test
Moeen Ali finished a brilliant campaign with a five-wicket haul as England beat South Africa by 177 runs in the fourth Test at Old Trafford on Monday to seal a 3-1 series win.
Victory, achieved with more than a day to spare, also saw Joe Root triumphant in his first Test series as England captain.
South Africa, set a huge 380 for victory, were bowled out for 202 shortly after tea on the fourth day when Moeen took two wickets in two balls to remove Morne Morkel and Duanne Olivier.
That gave the off-spinner a return of 5-69 in 19.5 overs and 25 wickets in total in a series where he also scored 252 runs.
"This series I have felt more consistent with bat and ball, especially ball. I felt good rhythm after the first game. I contributed with the bat a couple of times," Moeen told BBC Radio's Test Match Special.
"In general, I'm very pleased," the 30-year-old Worcestershire all-rounder added.
This result meant England had won their first home Test series against South Africa since 1998.
It was also just South Africa's second defeat in 20 away Test series, their other overseas campaign reverse in that sequence coming against India in 2015/16.
"I'm very pleased, a fantastic effort," an elated Root said. "We knew the target was a lot of runs and we set off brilliantly with the new ball."
South Africa, 43-3 at lunch, saw Hashim Amla (83) and captain Faf du Plessis (61) put on 123 for the fourth wicket.
But Moeen then took three wickets for five runs in 11 balls - including the prize wicket of Amla - as the Proteas collapsed from 163-3 to 173-6.
"Broad and Anderson are relentless and our batting line up wasn't strong enough for them," Du Plessis said after a match that seemed set to mark the end of Russell Domingo's tenure as South Africa coach.
"To lose Hashim and then the cluster of wickets was disappointing."
Graham Caygill: England's top order must fire if they want to win series
Earlier, Moeen, both Man of the Match and Man of the Series, made 75 not out off just 66 balls in England's second innings 243, having been dropped on 15.
That left South Africa facing a mammoth chase, with no side having made more to win in the fourth innings of a Test at Old Trafford than England's 294-4 against New Zealand in 2008.
South Africa's already difficult task was not helped when they lost both openers, leaving them at 18-2.
Dean Elgar, who made a gritty second-innings hundred in England's 239-run victory in the third Test at The Oval, fell for 5 on Monday when caught behind off Stuart Broad.
Heino Kuhn, struggling to cement his Test place, repeatedly played and missed before, on 11, edging James Anderson, again bowling from the newly-named James Anderson End, to Cook.
Temba Bavuma again battled hard until, from the last ball before lunch, he was given out caught behind on review off Toby Roland-Jones.
Amla completed a 100-ball fifty with his ninth four, a pull off Ben Stokes.
He then twice forced Stokes off the back foot for two stylish offside fours before driving Moeen for six.
But with South Africa 163-3, Amla missed an intended whip shot off Moeen and was lbw, although England, for the second time on Monday, had to first review umpire Kumar Dharmasena's original not out decision.
No replays were required when Quinton de Kock (1) edged a drive off Moeen to Alastair Cook in the slips.
And 173-5 became 173-6 when Theunis de Bruyn fell for a duck, nicking Moeen to slip fielder Stokes.
The end came quickly for South Africa, 182-6 at tea.
Du Plessis, who played at Old Trafford for Lancashire, had added just one to his tea score when he was caught behind off Anderson, England's all-time leading Test wicket-taker.
Anderson, who finished with 3-16, then had Kagiso Rabada caught in the covers.
Moeen, appropriately, finished the match with Morkel holing out for a duck before Olivier, also out for nought, was taken by Stokes at slip.