In the final, Bengal will lock horns with Mumbai on February 2nd. Bengal won the Rani Trophy twice - once in 1939 and then in 1989 under Sambaran Banerjee.
Beginning the day at 72 for 2, Bengal duo Manoj Tiwary and Abhishek Jhunjhunwala, both of whom had a dream run this Ranji season continued with their honeymoon with a deciding 150-run partnership in the third wicket that tilted the match in favour of Bengal.
While Manoj played a flamboyant innings embellished with 24 hits to the fence and two towering sixes of veteran off spinner Sunil Joshi, Abhishek played the second fiddle scoring 54 of 189 balls with the help of seven boundaries.
The post-lunch session saw the Bengal batsmen opening up and Manoj hit consecutive boundaries off Akhil to reach 90. The century came off a square drive of 176 balls.
The next 51 runs was scored in a hurry, studded with six boundaries and two sixes.
Meanwhile, Abhishek was trapped leg before playing across a line of a delivery from Sunil Joshi that fell in line with off stump and straightened.
But by then the fate of the match was decided and Bengal reached the stipulated target of 360 with Deep Dasgupta remaining unbeaten on 19 after Rohan Gavashkar went back cheaply on 12.
Bengal met Mumbai six times before but lost on all ocassions.
Manoj hit his third century of the season, while Abhishek hit his third half century of the season, scoring their respective hattricks in first class cricket.
Following the match, Bengal coach Paras Mhambrey said he was happy with the way the boys played and hoped they would continue with the good work in the final.
He said he was aware that Mumbai was a formidable opposition but Bengal would do their best.
Bengal captain Deep Dasgupta was jubilant having led the side to two Ranji Trophy final on a trot.
Last time a session's bad play against Uttar Pradesh cost them dearly to miss the trophy. The team had learnt from the mistakes and would handle the pressure better.
''We always play better when we play away. Mumbai is a tough opposition but we will give our best,'' he said and was all praise for the entire team especially the pace duo of Sourav Sarkar and Ranadeb Bose, who had raised their level of their performance this season.
Venkatesh Prasad said, ''Manoj and Abhishek took the match away from us. The key to this match was taking a few early wickets.'' He, however, said Karnataka was a young side and hoped the team would evolve into a better side having learnt from its mistakes.
He had a special word of appreciation for Ranadeb and Sourav, saying they bowled brilliantly and looked to have a very bright futute.
The Ranji Trophy final match between Mumbai and Bengal will be played at the Wankhede Stadium in Mumbai from February 2 to 6. and the match will be telecast live on Neo Sports.
K Hariharan (Delhi) and G A Pratapkumar (Chennai) will be the umpires. A Y Gokhale (Mumbai) will be the third umpire and B Raghunath (Bangalore) will be the match referee.