Legendary Penn State Coach Joe Paterno FIRED!!

Penn State football coach Joe Paterno is not untouchable, after all -- the university's board of trustees voted late Wednesday night to fire Paterno ... effective immediately.

The living legend, known as JoePa, announced early Wednesday that he would retire at the end of the season in the wake of the child sex abuse scandal that began with the arrest of Paterno's former assistant coach Jerry Sandusky.

In announcing his retirement, Paterno -- who's been PSU's head coach for 46 years -- said the trustees should "not spend a single minute discussing my status. They have far more important matters to address."

PSU President Graham Spanier was allowed to resign.

Paterno and Spanier are just two university officials who have been under fire for not going to police with their knowledge of Sandusky's alleged sex abuse incidents with young boys ... some dating back to 1994.

Hundreds of students are rallying on the Penn State campus -- many chanting support for Paterno.

2:41 AM PT At 2:00 ET, cops clad in riot gear issued a dispersal order to immediately leave the downtown area and the Old Main, and the students went home ... but not before some students turned over a TV microwave truck and tore down some street signs and a light post. Some students also set off fireworks, while chanting, "F**k the trustees."

10:00 PM PT Student rallies are getting violent -- a local CBS news van was tipped over and street signs torn down. Police in riot gear are trying to disperse the crowds.