Will Ferrell serenades graduates

Will Ferrell has received a standing ovation from thousands of university students after serenading the cohort at their graduation ceremony.

The 49-year-old actor returned to his old stomping ground at the University of Southern California to deliver the commencement speech for the Class of 2017 on Friday.

He gave a moving speech where he urged the graduates to listen to "trust your gut" and not let fear get in the way of their brimming potential before breaking out in song.

"I will always love you, Class of 2017," he sung, covering Whitney Houston's cover of Dolly Parton's classic ballad.

Students took to Twitter to share the wise words the famed actor bestowed upon them about his own indecision at their age.

"Yes, I was afraid. You're never not afraid. I'm always afraid. I was afraid to write this speech.

"I'm still afraid. But "what if" outweighed that.

"My fear of failure never approached in magnitude my fear of what if."

Farrell – who graduated USC in 1990 with a degree in Sports Information - also received an honorary degree alongside actress Helen Mirren.