The win gave the Lovech-based side an unassailable seven-point lead over CSKA Sofia, who came from behind to demolish third-placed city rivals Lokomotiv 5-1, with two matches remaining.
Litex top the standings with 64 points, followed by CSKA on 57. Lokomotiv are third on 52.
CSKA and Levski Sofia, the two most popular clubs in the Balkan country, have won nine titles between them in the last decade and 52 in total since CSKA's foundation in 1948.
Litex, champions in 1998 and 1999, became only the second team to upset the balance of power this century after Lokomotiv Plovdiv's triumph in 2004.
Litex, who sealed a place in next season's Champions League qualifying rounds, opened the scoring six minutes before the interval when French striker Wilfried Niflore headed in Brazilian winger Tom's cross.
Doka Madureira doubled Litex's lead early in the second half while Niflore put the game beyond doubt in the 81st minute with another firm header.
"We were the best team throughout the championship and we deserve the title," said delighted Litex coach Angel Chervenkov after the win in Plovdiv.
A late goal by midfielder Vladimir Gadzhev gave outgoing champions Levski Sofia a 1-1 draw at Cherno More Varna to keep alive their chances of qualifying for next season's Europa League.
