The left-handed opener smashed a 47-ball 89 to help Bangalore post a solid 185-4 after being put in to bat in the night game at the M.A. Chidambaram Stadium.

Last year's finalists Mumbai reached 142-8 in 20 overs.

New Zealand spinner Daniel Vettori took 3-19 while pacer Sreenath Aravind and left-arm spinner Syed Mohammad chipped in with two each.

Bangalore, finalists in 2009, meet defending champions Chennai Super Kings in the final on Saturday.

In-form Gayle hit nine fours and five sixes and put on 113 for the opening wicket in 10.3 overs with Mayank Agarwal (41) to give Bangalore a spectacular start.

Gayle, who hit two centuries this IPL season, lashed Abu Nechim for a six and three fours as the medium-pacer went for 27 runs in the opening over of the innings.

Gayle reached his third fifty with a fierce pull to the fence off pacer Kieron Pollard and then lashed a six off Nechim as Bangalore raced to 111 without loss after 10 overs.

“Lasith (Malinga) and Harbhajan (Singh) are their key bowlers so I was looking to be a bit tentative against them,” Gayle said after picking up his sixth man of the match award of the season.

“The outfield was very quick and wicket was good to bat on, it held up a bit when they chased, so we don't know what to expect tomorrow,” he added.

Agarwal was caught at long on while attempting to flat-bat Pollard.

Gayle, the season's leading run-getter with 608 runs, hit two successive sixes off Harbhajan before he was caught at long on by James Franklin while attempting to hit pacer Munaf Patel with the score at 148 in 14.4 overs.

“It is a continuation of how we have played most of the season,” Bangalore skipper Vettori said. “It's certainly not easy to bowl to Gayle, he has been a great asset for us,” he added.

Virat Kohli fell for eight playing-on to Nechim and Patel had Luke Pomersbach caught by Lasith Malinga at short third-man for four to apply the brakes on Bangalore.

However, AB de Villiers hit a 15-ball 21 to help Bangalore finish strongly.

Medium-pacer Sreenath Aravind dismissed Aiden Blizzard for 10 and Harbhajan, promoted as pinch-hitter, for 13, but skipper Sachin Tendulkar hit a 24-ball 40 with seven fours to keep Mumbai in the hunt.

Left-arm spinner Syed Mohammad took the key wicket of Tendulkar, stumped, to trigger a collapse as Vettori dismissed Rohit Sharma (13), Ambati Rayudu (0) and Pollard (3) in quick succession to help Bangalore take a firm grip on the match.

Left-arm seamer Zaheer Khan bowled Franklin for 16 and Mohammad dismissed Malinga for seven for his second wicket of the match.

“I thought the way Gayle started, that set the tone for them,” Tendulkar said. “We came back strongly in the last ten overs, they may have ended going above 200.

“This is a high-scoring game, it was within our reach. I thought it was a good track, it was coming on nicely, but in the middle overs we got stuck. The middle order, I felt, could have been more consistent, but it could not happen.”

Bangalore Royal Challengers 185-4 in 20 overs (Chris Gayle 89, Mayank Agarwal 41; Munaf Patel 2-27) def. Mumbai Indians 142-8 in 20 overs (Sachin Tendulkar 40; Daniel Vettori 3-19).