Downesia abdominalis is a species of beetle of the family Chrysomelidae. It is found in India (Sikkim).
Adults reach a length of about 6 mm. They are deep black and glossy, with a reddish-yellow abdomen. The antennae are longer than in most other Downesia species. The elytra are rather finely dotted in the double rows, the first two joined before the middle.
No host plant has been documented for this species.