The ruby tetra (Axelrodia riesei) is a species of freshwater fish in the family Characidae.

It is endemic to the Río Meta, Colombia, South America.

Ruby tetras grow up to 3 cm (1.2 in) to 3.5 cm (1.4 in) long.

Named in honor of tropical-fish exporter William Riese, who collected the type specimen.

This Characidae-related article is a stub.