In just a few hours the 34-hour rally will kick off in Kuala Lumpur, Kuching and Kota Kinabalu, which is expected to last until just before the stroke of midnight tomorrow on Merdeka eve.
Tens of thousands are expected to attend, despite police declaring the rally and its signature yellow T-shirts illegal.
The last Bersih rally in 2012 managed to attract over 100,000 people, who flooded downtown KL to call for clean and fair elections.
This year's rally comes amid growing anger at Prime Minister Najib Abdul Razak over various scandals including 1MDB, and the RM2.6 billion banked into his personal accounts claimed to be donations from the Middle East.
The rally will call for his resignation, as well as four demands:
Asking Najib to step down is not one of them, but that appears to be the clarion call by most rally-goers.