3:19 PM PT -- ROD SMART HAS BEEN FOUND SAFE!!

Family and police sources tell us Smart has been located and he's safe.

We're told Smart is surrounded by family and in the process of getting professional treatment.

Story developing ...

Rod Smart -- who shot to fame in the XFL using the nickname "He Hate Me" -- has gone missing and his family is extremely worried for his safety.

The Lancaster County Sheriff's Office in South Carolina has issued a Missing Person Advisory -- noting 42-year-old Smart was last seen on June 12 around 10:30 AM.

Cops say his family is "worried about his safety and well-being" -- adding, "It is unusual for him to be out of touch for this long."

He was last seen driving his silver 2016 Nissan Maxima with North Carolina tags.

Rod Smart -- real name Torrold Smart -- was a star running back at Western Kentucky back in the day ... and joined Vince McMahon's XFL football league when he wasn't selected in the NFL Draft.

In 2001, Smart was signed by the XFL's Las Vegas Outlaws -- which encouraged players to select a fun WWE-style nickname to rock on their jerseys ... and Smart famously picked, "He Hate Me."

Why the nickname? Smart told reporters at the time, "Basically, my opponent is going to hate me. After I win, he's gonna hate me."

Smart was so good in the XFL, he got looks from NFL teams and eventually signed with the Carolina Panthers ... where he played from 2002 to 2005.

After his football career, Smart reportedly worked as a personal trainer and a high school guidance counselor.