Ratana was passionate about rugby and was head coach of the East Grinstead club in Sussex.
Within a few hours, £55,494 ($106,387) had been raised. The foundation's target is £100,000 ($191,000) by Monday morning NZT.
"What an amazing day!," the foundation's official Twitter page tweeted.
Among those to wear their Matt Ratana Rugby Foundation rugby jerseys with pride were England rugby players, broadcasters and Met Police commissioner Dame Cressida Dick.
Several high-profile rugby players posted photos in their new foundation jerseys, flashing four fingers in solidarity with the foundation's Twitter handle @Try4Matt.
Former England rugby international Will Greenwood wrote that he was "delighted to be taking part" and urged others to join him.
Fellow former England cap Chris Robshaw also showed his support, as did England women's team stalwart Tamara Taylor and rising star former u20 England lock Joel Kpoku.
Others to post photos in their foundation jerseys included former Harlequins and Sale Sharks centre Mel Deane, Saracens' Alex Lewington, Leicester Tigers' Richard Wigglesworth and former Scotland rugby international Kenny Logan and his TV presenter wife, Gabby Logan.
Broadcaster Piers Morgan, who has 7.6 million Twitter followers, tweeted that he was "honoured to be taking part in the MRRF Challenge to celebrate the launch of The Matt Ratana Rugby Foundation".
Dick, who described Ratana at his funeral as an inspiration to others during his life and who would "remain so for generations to come", also backed the fundraiser, posing in a foundation polo top and encouraging others to "get involved and show your support".
"What amazing support we've had!," the foundation wrote, re-tweeting the post.