Gayle cracked 17 fours and a six as West Indies, without the injured Brian Lara, overhauled a modest Zimbabwe total of 154 all out in the 34th over to win the final league match by eight wickets.
West Indies finished on 155 for two wickets and will meet Sri Lanka in the final Wednesday.
Gayle who took the Man-of-the-Match award smashed 24 runs off two overs from Gary Brent as he raced to his half-century off as many balls with 10 fours and a six.
He was dismissed with the West Indies total on 121 when he was caught in the outfield by Henry Olonga off Douglas Marillier.
West Indies also lost the wicket of Gayle’s opening partner Daren Ganga for 12 when he nicked a delivery from Heath Streak to Andy Flower behind the stumps in the fifth over of the innings. It was the compact opener’s first failure in the competition after scoring half-centuries in his three previous innings.
Ramnaresh Sarwan (30) and Ryan Hinds (16) saw West Indies through without any further loss.
Earlier, Trinidad’s right-arm medium-pacer Darryl Brown took three wickets for 21 runs on his One-day International debut to help dismiss Zimbabwe for 154.
Brown, a late developer at 27 years with only five first-class games behind him, took the wickets of Trevor Gripper (4), Flower (21) and Marillier (5) in an impressive bowling performance that put West Indies in a position to win and qualify for the final.
Asked to bat first on a pitch where 474 runs were scored Saturday in the Sri Lanka-West Indies game, Zimbabwe’s top order gave a pathetic display as they collapsed to 53 for seven.
Their final total was achieved through the eighth wicket pair of former captain Streak and Travis Friend who added 60 off 101 balls.
Streak hit a fighting half-century to top score with 57 off 88 balls hitting one six and five fours before being caught at long-off as he tried to push the scoring rate up in the final overs.
Friend made 22 before Gayle had him stumped by Ridley Jacobs then Gary Brent hit out freely to score 19 before falling to West Indies captain Carl Hooper.
Scoreboard
ZIMBABWE:
D.D. Ebrahim lbw b Collymore 3
G.W. Flower b Collins 3
S.V. Carlisle c Jacobs b Collins 1
A. Flower lbw b Brown 21
C.B. Wishart run out 6
T.R. Gripper c Jacobs b Brown 4
D.A. Marillier c Hooper b Brown 5
H.H. Streak c Collins b Collymore 57
T.J. Friend st Jacobs b Gayle 22
G.B. Brent b Hooper 19
H.K. Olonga not out 0
EXTRAS (LB-3, W-7, NB-3) 13
TOTAL (all out, 49.2 overs) 154
FALL OF WKTS: 1-7, 2-7, 3-9, 4-24, 5-37, 6-45, 7-53, 8-113, 9-145.
BOWLING: Collins 10-0-24-2 (2nb, 1w); Collymore 10-1-26-2 (1w); Brown 10-3-21-3 (2w); Hooper 9.2-1-30-1 (3w); Hinds 5-0-27-0 (1nb); Gayle 5-0-23-1.
WEST INDIES:
D. Ganga c A. Flower b Streak 12
C.H. Gayle c Olonga b Marillier 85
R.R. Sarwan not out 30
R. Hinds not out 16
EXTRAS (B-2, W-7, NB-3) 12
TOTAL (for three wkts, 34 overs) 155
FALL OF WKTS: 1-15, 2-121.
DID NOT BAT: C.L. Hooper, M.N. Samuels, R.L. Powell, R.D. Jacobs, C.D. Collymore, P.T. Collins, D. Brown.
BOWLING: Streak 6-2-16-1 (2w); Friend 5-0-26-0 (5w); Olonga 6-0-49-0 (3nb); Brent 2-0-24-0; Marillier 8-2-32-1; Gripper 7-4-6-0.—Reuters