Police discovered the grow of more than 6,000 plants on a residential road near the M6, with officers at the scene describing it as the "biggest yet".
The plants, worth around £6 million at street value, were found growing across 40 rooms in a large building on Slaney Road on Friday.
A large number of armoured cables powering the growing equipment were also found.
Nobody was inside the building when police arrived and nobody has been arrested in connection with the drugs farm.
Cannabis grows are regularly uncovered by police at empty houses and industrial sites across the Black Country.
Last year a factory worth around £3m was uncovered inside the old Kenrick Building next to the M5 in West Bromwich and was also thought to have been one of the biggest ever discovered in the region.
A spokesman for West Midlands Police, said: "We were called to reports of a suspected cannabis factory at a property on Slaney Road, Walsall just after 9.30am last Friday.
"The property was searched and a cannabis farm was found inside consisting of 6,000 plants.
"The site was emptied and made secure by officers.
"Our specialist Cannabis Disposal Team have been clearing the scene and working with Western Power to make the site safe as the electricity had been bypassed.
"Anyone with any information can message us via live chat at west-midlands.police.uk, call 101 or speak to Crimestoppers anonymously on 0800 555 111, quoting crime number 20/717906/21."
The investigation is continuing.