Officials found documents showing that the club, named after Bulgarian revolutionary hero Vasil Levski, was established by a group of teenagers in Sofia on May 10 1911, rather than on May 24 1914, the year shown on the club's emblem.
Ambitious plans to commemorate the centenary are underway and the 26-times champions hope to celebrate with another league title if they can topple current leaders Litex Lovech by the end of the season.
"We'll inform (European governing body) UEFA and we'll change the year of foundation on our club's emblem," Levski president Todor Batkov told reporters after the annual meeting of the joint-stock company.
"No doubt, we'll celebrate our centenary on May 10 and I hope we'll have double celebrations after winning the title."
The discovery was not welcomed by Slavia Sofia, who until now had been regarded as Bulgaria's oldest club after being founded in 1913.
"Someone is trying to misrepresent history," Slavia Sofia president Ventsislav Stefanov said. "They say that God created Levski but they were created for Slavia to have someone to play against."
Levski played in red-and-yellow stripes until 1921 when they began to wear blue shirts and got the nickname The Blues.
Levski are second in the standings with 32 points, five points behind champions Litex during the mid-season break.
