Lan Cheng-lung (Chinese: 藍正龍; Pe̍h-ōe-jī: Nâ Chèng-liông, born March 1, 1979), also known as Blue Lan, is a Taiwanese actor and film director.

Lan was born in Yilan, Taiwan. He started his career as a commercial model, and made his acting debut in 2000. He gained attention for a small role as Ya-men in Meteor Garden and went on appearing in many popular films and dramas, including Night Market Hero (2011) and The Wonderful Wedding (2015).

Lan was in a high–profile relationship with actress Barbie Hsu from 2001 to 2005. In 2006, he dated Yvonne Yao for three months, followed by a two-year relationship with his non-celebrity girlfriend Lin Xinru until 2008. In late 2009, he briefly dated Easy Fortune Happy Life co-star Jocelyn Wang.

He met Jade Chou in 2000. The two began dating in 2011 and married in May 2014. They have a daughter, born in May 2015 and a son, born in October 2016. They divorced in 2023.