Free Money Day is a global social experiment held annually on September 15, the anniversary of the Lehman Brothers' 2008 filing for bankruptcy.

Founded in 2011 by Donnie Maclurcan,[2] co-founder and co-director of the Post Growth Institute, Free Money Day is a social experiment that is meant to explore people's attachment to money and remind people that it must freely circulate in a successful economy, as noted by Maclurcan:[3] "Just like any system in the human and eco-sphere requires circulation, whether it's nitrogen or oxygen flowing through our ecology, whether it's blood flowing through our bodies.

Free Money Day is an initiative of the Post Growth Institute (PGI), an international, not-for-profit organization leading the shift to a world where people, companies and nature thrive together within ecological limits.

The PGI works collaboratively to develop ideas, programs, events and alliances that promote the equitable circulation of money, power and resources in our local communities and global economy.

This has included giving out money to strangers in exchange for them listening to their music,[4] organizing a free sewing workshop, or a video store handing out free movie rentals to customers.