Virenque finished the grueling 137-mile climb up Mount Ventoux in 5 hours, 43 minutes and 26 seconds. The Frenchman finished 1 minute, 58 seconds in front of Russian Alexandre Botcharov and moved into 10th place in the overall standings.
It was likely a satisfying win for Virenque, who missed last year's Tour while serving a nine-month suspension due to drug use. It was the fifth overall stage win in his career.
Armstrong finished third in Sunday's stage, but increased his overall lead over Spaniard Joseba Beloki to 4 minutes, 21 seconds.
The three-time defending champion at the world's most famous cycling race, Armstrong captured his 14th career stage win Friday.
Though the finish in Paris remains seven days away, Armstrong is in prime position to ascend to the upper echelon of cycling royalty. He is looking to join France's Jacques Anquetil (1961-64) and Bernard Hinault (1978, 1979, 1981, 1982, 1985), Belgium's Eddie Merckx (1969-72) and Spain's Miguel Indurain (1991-95) as the only cyclists to win the race more than three times.
Armstrong already is recognized as among the world's most courageous athletes after battling back from testicular cancer to capture the 1999 event. In 2000, he cemented his place among cycling's all-time greats, becoming the first American since three-time champion Greg LeMond (1986, 1989 and 1990) to claim back-to-back titles.
Tuesday's 15th stage is a 140.640-mile trek from Vaison-la-Romaine to Les-Deux Alpes. It is the longest stage of the tour.