Roger Federer and his wife Mirka have donated 1m Swiss francs (£857,000) "for the most vulnerable families in Switzerland" and have called on others to add their support.
Because of the coronavirus pandemic, Switzerland has imposed a ban on all private and public events and has closed all non-essential businesses until at least 19 April.
"These are challenging times for everyone and nobody should be left behind," Federer, 38, wrote on Instagram.
"Our contribution is just a start.
"We hope that others might join in supporting more families in need. Together we can overcome this crisis!