The victim was found in the Bayview District near Third Street and La Salle Avenue after the shooting was reported at 4:11 p.m.
The teen was rushed to a hospital, but succumbed to his wounds. Authorities have not identified him.
Police have not announced any arrests or provided information about potential suspects.
Anyone with information about the homicide is asked to call the SFPD tip line at (415) 575-4444 or to send a tip by text message to TIP411 with "SFPD" at the start of the message.