"Tennis is a very popular sport and, so as far as I know, Roger Federer has been chosen to carry the Swiss flag and Rafa Nadal will lead the Spanish delegation at the opening ceremony in London," Tarpishchev, a member of the International Olympic Committee, was quoted as saying by local media.
The Russians have broken with tradition by choosing Sharapova, who won the French Open title last weekend.
Carrying the flag is considered a great honour in Russia and, until now, it was given only to famous athletes, mostly men, such as Greco-Roman wrestler Alexander Karelin and swimmer Alexander Popov, who have won numerous Olympic titles.
"Growing up in Russia, tennis wasn't a big sport back then. It was all about being an Olympian."
The Olympic tennis tournament will be played on the grass courts at Wimbledon where, as a 17-year-old, Sharapova stunned Serena Williams in the 2004 Wimbledon final to win her maiden grand slam title.
Her win in Paris gave Sharapova the full set of four grand slam titles.