The five-piece post-hardcore band formed in 1999 and released four studio albums over the last ten years.
The group will perform their 2002 debut album Ideas Above Our Station in full for their last ever gigs in November.
The gigs will take place on November 23 at the Manchester Academy 2 and on November 24 at London's HMV Forum.
Hell Is For Heroes will also reunite for the pair of gigs after splitting in 2008. They will play their debut album The Neon Handshake in full.
Hundred Reasons wrote on their Facebook page: "Dream lineup - bands we love, people we love. Been a while in the planning, this, but we're seriously bloody excited about it.
"This is the final outing for everyone involved, so we hope you'll join us for a properly good send-off."
Hell Is For Heroes added: "We a can confirm that we are coming out of rock 'n' roll retirement for two very special shows this November."
Alternative rock band Cable will also perform at the gigs, with tickets going on sale tomorrow (June 27) at 9am.
Hundred Reasons' debut album was their most successful, reaching number six in 2002. Their biggest hits included 'Silver' and 'If I Could'.
Watch Hundred Reasons perform 'Remmus' live in 2004 below: