Isognathus swainsonii is a moth of the family Sphingidae.

It is found from French Guiana, Peru and Brazil to Bolivia.

It is similar to Isognathus leachii, but the forewing upperside has more white scaling, there are interrupted white vein-streaks on the distal half of the wing, the basal patch is thinner and the marginal spots at the ends of veins are larger and paler grey.

The larvae have been recorded feeding on Plumeria acuminata.

They have long tails and are very colourful, suggesting they are unpalatable to birds.