Officers seized 2,000 plants and sophisticated hydroponic growing equipment when they raided a disused Gala Bingo Hall in Kettering.
Northamptonshire Police said the operation could have generated around £2.8m each year.
Police became suspicious when officers said they could smell the drug coming from the derelict building, in Kettering High Street, which closed in January.
Thermal imaging also revealed heat sources coming from the building despite it lying empty.
Around 25 officers, along with dogs, stormed the building at 10.30am on Friday.
“This is a significant find that will disrupt organised crime groups and the distribution of cannabis locally and further afield,” said PC Colin Gray, from the force’s proactive team.
“It is one of the largest I have seen even when compared to a site we found in Corby earlier this year.”
In June 2018, the Institute of Economic Affairs (IEA) estimated the UK’s illicit cannabis market to be worth £2.5bn each year, distributed to just over three million users of the drug.
Mr Gray said: “These crime groups blight society by manufacturing and selling controlled drugs in Northamptonshire.
“We will never stop trying to bring them down and this type of activity will continue.”
Nobody was inside the cannabis factory but the bingo hall’s kitchen had been in use.
The plants were coming of age and only about three weeks away from being ready for harvest and distribution.
The IEA’s 2018 report calculated the UK’s total cannabis consumption at 255 tonnes each year, meaning that the drug would be worth £1bn in tax revenue alone if legalised.
An influx of super-strength cannabis has been blamed for London having number the highest rate of psychosis on record in Europe.