The 2006 Top League Challenge Series was the 2006 edition of the Top League Challenge Series, a second-tier rugby union competition in Japan, in which teams from regionalised leagues competed for promotion to the Top League for the 2006–07 season. The competition was contested from 15 to 28 January 2006. Coca-Cola West Red Sparks and IBM Big Blue won promotion to the 2006–07 Top League, while Honda Heat, Kintetsu Liners, Kyuden Voltex and NTT Communications Shining Arcs progressed to the promotion play-offs.