Gayle???s score was the fastest fifty (taking 17 balls) by a West Indian in T20 cricket as the visitors chased down the Proteas target of 166.
Rilee Rossouw had earlier top-scored for South Africa with 51 not out from 40 balls, having been dropped on 30 by Sheldon Cottrell in a poor showing from the visitors in the field.
But with a full-strength West Indies side facing a South African outfit without the rested AB de Villiers, Hashim Amla, Dale Steyn and Morne Morkel, a respectable score of 165-4 wasn???t to be enough.
Starting with one run from his first six deliveries, Gayle pummelled his next 11 for a boundary a ball ??? with the exception of one which went for two ??? to bring up his fifty.
The next ball South Africa got a breakthrough, Imran Tahir (3-28) getting Dwayne Smith (20) lbw attempting a reverse-sweep in his first over.
So it made Gayle???s decision to play the same shot to the same bowler in his third over ??? having dispatched him for two more straight sixes earlier in the over ??? all the more baffling.
Tahir also picked up Samuels for 41 as the West Indies somewhat stuttered over the finish line, losing four wickets for 17 before Kieron Pollard hit the winning runs with four balls to spare.
After dominating the Test series between the two, South Africa rested their stars with five ODIs following these three T20s ??? and a World Cup round the corner ??? fielding an inexperienced XI.
An example being opener Morne van Wyk, the 35-year-old wicketkeeper bastman playing in only his fourth T20I and four years after his last.
Windies opening bowlers Sheldon Cottrell (2-33) and Jason Holder (1-20) restricted the hosts early with Holder picking up van Wyk (17) edging to Chris Gayle at slip ??? a rare sight in T20 cricket ??? after Cottrell dismissed his opening partner Reeza Hendricks (12) lbw.
South African captain, Faf du Plessis, got the innings going with a quick-fire 38 from 20 balls containing five fours and two sixes.
When he departed, Rossouw got good support from David Miller (24) in a 48-run partnership but Miller wasn???t his usual explosive self, with only one four in his 21-ball stay at the crease and South Africa???s score proved not to be enough.