Ronnie Day (born Ronald Guglielmone Jr.; January 18, 1988) is an American songwriter from Redwood City, California.

He rose to the top unsigned artist position on both Myspace and Purevolume's music charts, and sales of his album skyrocketed.

In 2006, on his 18th birthday, Day signed with Epic Records, ending an industry-wide bidding war.

mtvU produced The Ronnie Day Project, an episodic video series based on the music from his debut album.

The series was directed by Joshua Caldwell, who won an MTV Movie Award for Best Film on Campus.