'16 & Pregnant' Star Whitney Purvis Arrested for Involuntary Manslaughter

Whitney Purvis is in police custody after being arrested for felony involuntary manslaughter involving a fatal overdose ... TMZ has learned.

The "16 and Pregnant" star was busted Monday by sheriff's deputies in Floyd County, GA ... according to online records. The involuntary manslaughter charge is for intentionally distributing a drug called Tranq -- a combo of Fentanyl and Xylazine.

Cops say the Tranq caused the victim -- John Mark Harris -- to suffer a toxic overdose.

Whitney's arrest for Harris' death comes a little over a month after her teenage son, Weston, died of natural causes.

In addition to involuntary manslaughter, she was also arrested on 2 other charges involving controlled substances ... including possession with intent to distribute.

The former teen mom has been arrested three times before ... but for much less serious allegations. She got busted for allegedly shoplifting a pregnancy test, smashing up some electronics and failing to pay child support.

We reached out to Whitney's camp ... so far, no word back.