Farrah Abraham -- Hand In Hand w/ GIANT Male Porn Star

Farrah Abraham was gettin' super hands on with one of the biggest male porn stars in the biz yesterday ... James Deen ... fueling rumors that he's the co-star in the "Teen Mom" star's sex tape.

Farrah and James -- who, along with having genitals that resemble an elephant trunk, once starred in a mainstream movie with Lindsay Lohan -- were photographed walking into the offices of Vivid Entertainment yesterday.

The two were holding hands ... but it's unclear if they're dating ... or just simply friends with professional benefits.

Farrah previously told TMZ she's AGAINST the release of the tape and is considering legal action to stop the footage from going public.