'Amazing Race' Teammates Josh and Paul Were Once 'Big Brother' Enemies

The latest duo to join the new season of "The Amazing Race" once viciously competed against each other on "Big Brother," and now they'll be battling for $1 million.

TMZ has learned ... Josh Martinez and Paul Abrahamian are teaming up for the "Big Brother" mash-up season of 'Race.' They were on season 19 of 'BB,' which Josh ended up winning the $500k grand prize ... and Paul came in second.

Despite the fact Paul bitch slapped Josh while they were in the 'BB' house -- we're told they actually became good friends afterward. We'll see if that holds up though, while they race around the world.