Renee Zellweger plays the titular role in Judy, which is released in the UK next month.
Set in 1968, the film follows Garland as she was battling addiction issues and struggling financially.
“In 15 years at #TIFF I have never seen a standing ovation like the one for Renee Zellweger at Judy,” said Variety’s Jenelle Riley.
After sustained applause, Zellweger joked: “OK quit it – you’re messing up my make-up!”
The film sees Garland launch a residency in London as she tries to get her life and finances back on track. But she was in a fragile state of mind and behaving erratically in the final months of her life – something the film does not shy away from.
Garland eventually died of an overdose aged 47, six months after her London shows ended.
The film features flashbacks to her time filming The Wizard of Oz, which suggest her addiction issues started young and were not helped by those around her.
The audience response in Toronto follows warm reviews for the film from critics and is likely to put Zellweger in the frame for a potential Oscar nomination.
“Her transformation is quite astonishing here, and the extended sequences at the Palladium demonstrate her ability to recreate Garland’s physicality and mannerisms,” said Fionnuala Halligan in Screen Daily.
“The casting makes bittersweet sense,” added Guy Lodge in Variety. “A onetime American sweetheart who relinquished the burdensome title, she plays Garland, with palpable affection and feeling, as one who’s been over the rainbow and back again.”
Vanity Fair’s K Austin Collins said: “Judy isn’t visionary or perfect, but it convinces us of its ideas – and it’s a fine scaffolding for Zellweger, already a potential awards contender for reasons that seem obvious.”