A South Carolina prison nurse has been charged with having sex with an inmate — after a cellphone she smuggled in for him was found with graphic x-rated videos of them at it, according to an arrest warrant.

Courtney Williams, 36, was busted Wednesday over her nearly two-month relationship with an inmate who was “under her direct care and supervision,” according to the warrant seen by The Post.

She “used official access and authority to facilitate the conduct” and “planned sexual intercourse with the inmate in her workplace within the prison,” Richland County prosecutors said.

Williams smuggled in a cellphone for the unidentified inmate at the male-only Kirkland Reception and Evaluation Center, which he used to share 1,000 texts between March 30 and May 29.

They “exchanged sexually explicit messages in which [Williams] provided details of the sexual intercourse,” investigators said.

She allegedly sent explicit snaps and videos — including one where she was performing a sex act with him, according to the warrant.

“Communications confirmed that completed sexual intercourse with penetration occurred between [Williams] and the inmate,” it states.

“This is based on evidence obtained from digital forensic examinations of the inmate’s cell phone and the defendant’s cell phone, video footage, and statements.”

Just weeks after her alleged romance began, she resigned from her role with the South Carolina Department of Corrections amid a misconduct probe, WIS reported.

She recently worked as a nurse for the state’s Department of Juvenile Justice – but resigned earlier this month while under investigation, details of which were not released.

Williams has now been charged with first-degree sexual misconduct with an inmate and bribery, and faces 10 years in prison if convicted.