Former MMA star War Machine -- who is serving a life sentence for brutally beating his ex-GF -- got married behind bars ... and these aren't your typical wedding photos by a long stretch.
War Machine tied the knot with his longtime prison pen pal Ashley Farrington at Lovelock Correctional Center in Nevada ... taking a break from lockdown to say, "I do."
The convicted woman-beater slid a gold band on his new wife's finger -- the ring belonged to Ashley's grandmother. Hard to imagine this is what grandma had in mind.