Contador is the bookies' favourite for this year's race
Alberto Contador will be Astana's team leader in this year's Tour de France, which begins on 4 July.
The announcement means seven-times Tour winner Lance Armstrong, who returned to racing in January, will be one of the Spaniard's support riders.
"It's hard to find a better stage race rider than Alberto," said team manager Johan Bruyneel of the 2007 Tour winner.
"He has worked very hard, earning the right to represent our team as the leader in July."
Contador, 26, is expected to start strongly in the opening 15.5km time trial which opens the 2009 race in Monaco.
American Armstrong, 37, whose comeback ended a four-year retirement, will be one of seven Astana riders whose job is to maximise Contador's chances of victory through team strategy.
"I'm very happy with where Lance's form is leading up to the Tour", said Bruyneel.
"I think racing the Giro was a very smart decision and really prepared him for July. He is extremely motivated for the Tour de France."
Armstrong, 37, broke his collarbone in March but took part in the Giro, which he finished in 12th place overall, almost 16 minutes behind winner Denis Menchov of Russia.
Astana, seen as one of the strongest teams this year, had already announced a list of six Tour riders, including Ukrainian Yaroslav Popovych, the 2005 Tour's best young rider, and veteran mountain specialist Haimar Zubeldia of Spain.
The latest three additions to the team were Dmitriy Muravyev, the only Kazakh rider on the squad and a Tour newcomer, Portugal's Sergio Paulinho - a strong Contador ally - and Gregory Rast of Switzerland.