William Rast is a Los Angeles, California based clothing company founded by Justin Timberlake and Trace Ayala most known for their premium jeans.

On October 17, 2006 Justin Timberlake and Trace Ayala put on their first fashion show to launch their new William Rast clothing line. The label also produces other clothing items such as jackets and tops.

The name "William Rast" is a combination of Timberlake's grandfather's first name and Ayala's grandfather's last name.

William Rast denim has a signature embroidery on the back pockets that resembles a "V" with a slash across it.

William Rast Jeans can be seen on almost every episode of CW's Privileged worn by Joanna Garcia, who was engaged to co-founder Trace Ayala until early 2009.^{[citation needed]}

Johan & Marcella Lindeberg are the creative directors for William Rast.

In early 2011, the company formed a limited-time partnership with Target.

William Rast sponsored the #98 car of Dan Wheldon which won the 2011 Indianapolis 500.

In 2008, throughout the month of September, Timberlake starred as the fictional William Rast alongside supermodel Erin Wasson in a series of webshorts. They ranged in time from about 15 seconds to a minute and 45 seconds.

Justin Randall Timberlake (born January 31, 1981) is an American singer, actor, and businessman. He achieved early fame when he appeared as a contestant on Star Search, and went on to star in the Disney Channel television series The New Mickey Mouse Club, where he met future bandmate JC Chasez. Timberlake became famous in the late 1990s as the lead singer and youngest member of the boy band 'N Sync, whose launch was financed by Lou Pearlman.

In 2002, he released his debut solo album, Justified, which sold more than seven million copies worldwide. The album was a commercial success, spawning the hits "Cry Me a River" and "Rock Your Body". Timberlake continued his success with his second solo album, FutureSex/LoveSounds (2006), debuting at number one on the Billboard 200 chart, and produced the US number-one hit singles "SexyBack", "My Love", and "What Goes Around... Comes Around".

Timberlake has won six Grammy Awards and four Emmy Awards. His first two albums made him one of the most commercially successful singers in the world, each selling in excess of 7 million copies. He also has an acting career, having starred in films such as The Social Network, Bad Teacher and Friends with Benefits. His other ventures include record label Tennman Records, fashion label William Rast, and the restaurants Destino and Southern Hospitality.