LEGO Master Builders, father and son Dan and Chris Steininger from the US, were tasked with building the world's biggest - the spacecraft famously piloted by Han Solo (Harrison Ford) in Star Wars.
More than 2,000 fans were part of the occasion, building a five-metre wide Millennium Falcon from almost 250,000 LEGO bricks.
The fans also built a pair of two-metre high TIE fighters using nearly 80,000 bricks.
"What a way to celebrate May the 4th be with you!” said Dan Steininger. “Usually models the size of the Millennium Falcon can take more than a week to build and it was thanks to the Aussie fans that we were able to build a model of this size in such a short time.
LEGO Master Builders assemble the world's largest Millennium Falcon. (Supplied)
“It was very inspiring to see thousands of Melbournians come together, dress up, play and help build these iconic Star Wars vehicles – we certainly couldn’t have finished without them!”
The LEGO models will be only display at Westfield Southland, Victoria until May 10.
'May the 4th be with you'
Many are also marking Star Wars Day on social media with the tagline "May the 4th be with you", which is a play on the famous Jedi words, 'May the force be with you'.
