Carly Smithson (née Hennessy) (born September 26, 1983) is a singer, originally from Ireland, who is (as of March 2008) a semifinalist on the seventh season of American Idol.

Smithson released an album for MCA Records called Ultimate High in 2001 as Carly Hennessy, before taking her husband's last name. The album failed to find an audience despite good reviews and MCA Records spending over $2 million on the production and promotion of the album. The fact that the album was released on September 11th 2001 undoubtedly contributed to its low sales figures. Its commercial failure was documented in an article in The Wall Street Journal. Despite low record sales, she later won a Meteor Award in 2003 for Best Irish Female Singer.

Carly was signed to MCA records during the same time period that Randy Jackson was the senior vice president of A&R. Carly was at MCA in 1999. Randy started at MCA in 1998 and was there for 4 years.

Some of Carly's music was written by Danielle Brisebois, who has also written for Clay Aiken and Kelly Clarkson. One of the songs by Brisebois – "Just Missed The Train", originally recorded by Norwegian artist Trine Rein – was featured on both Smithson's album and Clarkson's 2003 album Thankful.

Before season seven, she auditioned in Las Vegas during the show's fifth season; she made it to Hollywood but was disqualified because her visa had expired.