Hemibrycon sanjuanensis is a species of characin from the upper San Juan River, Colombia.

The body is slender and long, with a short, compressed face and flexible lips.

In an example of sexual dimorphism, the rays of males' pelvic and anal fins are lined with small hooks.

A reddish spot can be observed on the ventral part of the base of the caudal fin.

[1] H. sanjuanensis is believed to be endemic to the upper San Juan River in Colombia.