Lay was born Zhang Yixing in Changsha, Hunan, China. In 2008, he was cast into S.M. Entertainment through the company's global casting system. Prior to joining S.M. Entertainment, Lay was a local child star in China, and made guest performances in various Chinese variety shows. In 2011, Lay briefly worked for SHINee in their concert tour as Jonghyun's dance replacement. Lay was formally introduced as a member on January 17, 2012.
In January 2015, Lay was ranked 5th on Baidu's "2014 Top 10 Most Popular Celebrities" list. In September 2015, he released his autobiography titled Standing Firm at 24, which broke several online book records. In July 2016, Lay was appointed by the Communist Youth League of China (CYLC) of Changsha as the publicity ambassador, the first celebrity to hold such title