Harkness Tower is a masonry tower at Yale University in New Haven, Connecticut. Part of the Collegiate Gothic Memorial Quadrangle complex completed in 1922, it is named for Charles William Harkness, brother of Yale's largest benefactor, Edward Harkness.

The tower was constructed between 1917 and 1921 as part of the Memorial Quadrangle donated to Yale by Anna M. Harkness in honor of her recently deceased son, Charles William Harkness, an 1883 Yale graduate. When the residential college system was inaugurated in 1933, the tower became part of Branford College.

Harkness Tower is 216 feet (66 m) tall, one foot for each year since Yale's founding at the time it was built. From a square base, it rises in stages to a double stone crown on an octagonal base, and at the top are stone finials. From the street level to the roof, there are 284 steps.