Sylvester Stallone’s 19-year-old half brother was viciously attacked Saturday night … and he’s lucky to be alive.

Dante Stallone, Sylvester Stallone’s half brother (Photo: Instagram)

We’ve learned Dante Stallone was on campus at Florida State in Tallahassee when 2 men brutally went after him.

We’re told Dante suffered a shattered jaw and a split palate, as well as broken and knocked out teeth.

Dante is the son of Frank Stallone, Sr. and his 4th wife.

Sly tells TMZ, “This is a wonderful young man, a straight-A student who would not cause any trouble,” adding, “It’s just so tragic and terribly sad.”

We’re told the assailants got away and cops are on the hunt.