Saint West Twitter War -- Rapper Loses to Kimye's Kid

Saint West, the rapper, lost his Twitter handle the day after Saint West, the baby, was introduced to the world -- but Kanye West and Kim Kardashian aren't behind the power move ... we're told.

When Kim announced her baby’s name, Twitter users flocked to @SaintWest and were surprised to see a Canadian rapper owned the page ... for a few more hours, anyway.

Sources tell TMZ ... Twitter told the rapper via email his handle would be modified to @SaintWest___ -- not because Kim demanded it, but because his last tweet was in 2011!

Twitter policy states you must tweet at least once every 6 months to be considered active. We're told the sudden flood of interest in the name is how Twitter realized the rapping Saint West was asleep at the tweetin' wheel.

His old handle was snatched up quickly -- but NOT by the Kardashians, we're told. The new mystery owner's not dumb though ... he/she quickly followed Kim's account.