The pair has dispensation to compete at London 2012 as host nation players, but have qualified by right for Rio.
Drinkhall, 26, and Pitchford, 22, helped England's men win bronze at this year's World Team Championships.
"We are delighted that Team GB have two qualified singles players for the first time in 20 years," said GB's table tennis team leader Simon Mills.
Drinkhall and Pitchford, who are ranked 60th and 51st in the world respectively, won a combined five medals at the 2014 Commonwealth Games.
Liam Pitchford and Paul Drinkhall have been selected to represent Great Britain at this summer's Rio Olympics.