The Tinkoff-Saxo team leader, who notched up his third Vuelta a Espana title on 15 September in Santiago de Compostela, Spain, announced his intention to do the difficult double while at an event in Italy.
"I have already spoken to Bjarne Riis and my coach and we have decided that my first goal of 2015 will be the Giro d'Italia", said Contador.
While ruling out a tilt at all three Grand Tours in a single season, Contador said that he decided on the Giro, Tour double in order to "take on a new challenge and have a new motivation."
The 31-year-old Contador first won the Giro in 2008 and again in 2011, only to have the latter result rescinded due to a doping ban.
The decision sets up a rivalry with 2014 Tour de France champion Vincenzo Nibali (Astana) who has also announced his intention to attempt the same feat.
Nibali won the Vuelta a Espana in 2010 and Giro in 2013, and is one of only six riders, including Contador, to have won all three Grand Tours in a career.
The last rider to win the Giro and Tour in the same year was the late Marco Pantani in 1998.
The 2015 Giro d'Italia will run from 9-31 May and begins with a team time trial in San Remo.