The Vertical Ray of the Sun (Vietnamese: Mùa hè chiều thẳng đứng, French: À la verticale de l'été) is the third feature film by Vietnamese-born French director Trần Anh Hùng. It was released in 2000 and is the final part of what many now consider to be Tran's "Vietnam trilogy."

The film centres on three sisters who live in present-day Hanoi: Suong is the eldest, then Khanh in the middle, and Lien is the youngest. The film takes place over the course of one month, starting on the anniversary of their mother's death and ending on the anniversary of their father's. Tran was inspired to make the film after visiting Hanoi during a break in the filming of Cyclo during the Christmas holidays in 1994.

This drama was lensed in Vietnam's capital, Hanoi, as well as in Hạ Long Bay and the village of Luoi Ngoc, Quảng Ninh Province.

The film's original score is composed by Tôn-Thất Tiết. Additionally, three songs of the noted Vietnamese songwriter Trịnh Công Sơn are interspersed through the film, as are songs by The Velvet Underground, Lou Reed, Arab Strap, and The Married Monk.

The Vertical Ray of the Sun was screened in the Un Certain Regard section at the 2000 Cannes Film Festival.