The two charities are each contributing $50m (£38.7m) and Mastercard is offering $25m (£19.3m) in seed funding for research to develop treatments, vaccines and diagnostic tools to combat Covid-19.
The Covid-19 Therapeutics Accelerator project will also coordinate research efforts and remove barriers to drug development, Wellcome said in a statement.
There are currently no approved treatments for Coronavirus. The project has been established to accelerate and evaluate new and repurposed drugs to deal with the outbreak through sharing research and coordinating investments.
The partners have committed to ensuring treatments are accessible and affordable, a statement said.
Jeremy Farrar, director of Wellcome, said: "Science is moving at a phenomenal pace against Covid-19, but to get ahead of this epidemic we need greater investment and to ensure research coordination. The Therapeutics Accelerator will allow us to do this for potential treatments with support for research, development, assessment and manufacturing.
"Investing now, at scale, at risk and as a collective global effort, is vital if we are to change the course of this epidemic. We welcome others to join us in this effort."
Mark Suzman, chief executive of the Bill & Melinda Gates Foundation, said: “Viruses like Covid-19 spread rapidly, but the development of vaccines and treatments to stop them moves slowly.
“If we want to make the world safe from outbreaks such as Covid-19, particularly for those most vulnerable, then we need to find a way to make research and development move faster. That requires governments, private enterprise and philanthropic organisations to act quickly.”