How Long Will I Love U (Chinese: 超时空同居) is a 2018 Chinese fantasy romantic comedy film written and directed by Su Lun, based on an idea by Xu Zheng who also produced the film. The film stars Tong Liya and Lei Jiayin, and tells a story about a young woman from 2018 and a young man from 1999 who become roommates after a spacetime merge inside their apartment.

Reportedly filmed on a ¥40 million budget, How Long Will I Love U grossed ¥900 million ($130 million) in China where it premiered on 18 May 2018. Foreign critics generally note the fine on-screen chemistry between Lei and Tong, who previously co-starred in the 2013 TV series Weaning.