The 2005 Top League Challenge Series was the 2005 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 2005–06 season. The competition was contested from 16 to 29 January 2005. Fukuoka Sanix Bombs and Secom Rugguts won promotion to the 2005–06 Top League, while Honda Heat and Toyota Industries Shuttles progressed to the promotion play-offs.