Justin Bartha is an American actor, known for his co-starring role as Riley Poole in the National Treasure films.

Bartha was born in Fort Lauderdale, Florida. His father, Stephen, is a real estate developer, while his mother, Betty, is a school teacher. He has one sibling, a brother named Jeffrey. Bartha is Jewish. His family moved to West Bloomfield, Michigan when Bartha was nine years old. While at high school, he muddled his way into acting after breaking his wrist trying out for the school's tennis team. After scoring a role in the local production of A Midsummer Night's Dream he formed a children's theatre group of 15 where he performed for children in hospitals and at elementary school. After he graduated from West Bloomfield High School in 1996, he set his sights on New York, eventually training at New York University's Meisner Extension. To quote his father, "Justin was born in Florida, raised in Michigan, but he's been a New Yorker all his life.”

He began his movie career behind the camera as a production assistant on the film Analyze This. His acting debut came a year later in a short film called Tag in 1999. He wrote and directed a short film, Highs and Lows, which was shown at the South by Southwest Film Festival in 2003. Additionally, for MTV he wrote, produced and starred in an MTV pilot called the The Dustin and Justin Show. He played a major role in the critically bashed Gigli and Carnival Sun before his co-starring role in National Treasure (2004) as Riley Poole. On December 19, 2007 Bartha appeared on the radio show Loveline to support National Treasure 2.

In 2006, Bartha had a supporting role in Failure to Launch and starred in the television sitcom Teachers which premiered on March 28th, 2006 on NBC, and was cancelled May 15, 2006 due to low ratings.

In November 2007, Bartha was cast in an indie comic-drama, Holy Rollers. His character lures a young Hasidic Jew into becoming an Ecstasy dealer. Filming is scheduled to begin in New York in the spring of 2008.

It has also been announced that Justin will star alongside Catherine Zeta-Jones in the new Bart Freundlich film, The Rebound. The romantic comedy is about a 25-year-old man (Bartha) who starts a romance with his older single mother neighbour (Zeta-Jones). The movie began shooting in April 2008 in New York, and finished in June.

Bartha will also be starring in a French film called Shoe At Your Foot, about a young man who loses his luggage on a trip to Paris. A young Frenchwoman finds the missing luggage and falls in love with him through his possessions.

Justin has been dating actress Ashley Olsensince May of 2008. Though there was a rumor of an engagement in October 2008, it was denied by Olsen's representatives. In the past, Justin has also been romantically linked with Lydia Hearst-Shaw.