The 33-year-old, who has started every one of his side's games this season, has been at the Spanish club since 2002 and the new deal will see him stay for another year
The 33-year-old has been at Bilbao since 2002 and was handed his debut by Jupp Heynckes in a 5-2 defeat at Villarreal in March of the same year.
Gurpegi was banned for two years in November 2003 after testing positive for nandrolone; the ban was initially suspended but his appeal was ultimately unsuccessful and the sentence was served from July 2006.
However, he returned in April 2008 and has re-established himself as a regular member of Bilbao's starting XI.
A statement on the club's website read: "Athletic Club and Carlos Gurpegi have signed a renewal whereby the player will remain until June 30, 2015."
The defensive midfielder commented: "Playing here is a dream and I am very grateful to the club. Everything has been easy and I am very happy."
Gurpegi has started every game for Ernesto Valverde's outfit this term, making 13 appearances in total to help the club to fifth place.
The 33-year-old will look to continue his ever-present record this season when Bilbao travel to Malaga after the international break.