Amphionides reynaudii is a species of caridean shrimp, whose identity and position in the crustacean system remained enigmatic for a long time.

It is a small (less than one inch long) planktonic crustacean found throughout the world's tropical oceans, which until 2015 was considered the sole representative of the order Amphionidacea, due to unusual morphological features.

In 1969 it was connected to a supposed adult form described earlier by Carl Zimmer (1904), not recognisable as a caridean shrimp, and in 1973 was Amphionides placed in its own order Amphionidacea by Donald I. Williamson,[1] i.e., at the same rank as the Decapoda and Euphausiacea.

The specific epithet reynaudii was given by Henri Milne-Edwards in honour of a friend of his, possibly Count François Dominique Reynaud de Montlosier.

[4] Based on molecular comparisons, the species was moved back to Decapoda and to the shrimp infraorder Caridea in 2015, while the adult stage still remains undiscovered.