Jang Yoon-ju (; born November 7, 1980) is a South Korean model, television personality, singer-songwriter and actress. Yoon-ju began modeling in 1997 when she was 17 years old, and became one of the most successful Korean fashion models, with a career spanning almost two decades. She also hosts Korea's Next Top Model, and won Best Radio DJ at the 2013 KBS Entertainment Awards for KBS Cool FM's Rooftop Radio. As a singer-songwriter, Jang has released two albums, Dream (2008) and I'm Fine (2012). She made her acting debut in 2015, playing a detective in Ryoo Seung-wan's crime thriller Veteran.
Jang is currently represented by ESteem Entertainment (SM Entertainment) as a model and by XYZ Studio as an actress.
In May 2011, Jang along with fellow models Kim Jae-wook, Ji Hyun-jung, Han Hye-jin and Song Kyung-ah, co-authored a book titled Top Model. It is based on their experiences in the industry and includes beauty, makeup and styling tips.