Paul Stretford, who himself is a millionaire, donated the money as part of a grass roots development scheme in Manchester's Moss Side area.
Fletchman, who is just six years of age and comes from Moss Side, is regarded by some as the British Serena Williams for the talent and calibre she has shown at a very young age.
Funding for her coaching classes has been a problem for her family, but Stretford's donation is a boost.
"Jhonayah is a very, very special talent," said Stretford. "But talent cannot thrive without the money to help it get where it needs to go."
Fletchman took to tennis aged just five on the courts at Alexandra Park and has won a number of junior tournaments, beating players older than her in the process.