Neimoidians were a humanoid species native to the planet of Neimoidia, while also settling wealthy colonies they named Purse Worlds, such as Cato Neimoidia. They had smooth noseless faces, mottled green-gray skin, and large red-orange eyes. In the waning years of the Galactic Republic, they ran the Trade Federation, a vast consortium of business interests. As such, they ended up joining the Confederacy of Independent Systems and helped start the Clone Wars. Neimoidians were related to the Duros species.

The Neimoidians were a sentient species of humanoid with two arms, two legs, a torso, and a single head. They had smooth, mottled green-gray skin and large, red-orange eyes with a pupil that split it horizontally. Some Neimoidians had a beige skin and the color could evolve over the years. For example, Nute Gunray had a gray skin at the beginning of the Clone Wars before turning green at the end of the conflict. Adult individuals were known to be tall, ranging from 1.9 to 2.11 meters. Neimoidians had long, bony hands with five pointed fingers, one of which was an opposable thumb. Although many Neimoidians were lean, obese individuals were not unheard of. They looked very similar to the Duros because the two species were genetically linked. In fact, the Neimoidian homeworld of Neimoidia was discovered and colonized by Duros. Over the millennia, the Duros of Neimoidia evolved because of the more humid atmosphere and heavier gravity of their planet.

The Neimoidians spent the first seven years of their life as «grubs,» maggot-like larvae that were forced to compete with each other over a limited food supply. It was possible that they never emerged from their maggot state because of a lack of food and became drones.

Neimoidians first appeared in the 1999 film Star Wars: Episode I The Phantom Menace, the first installment of the Star Wars prequel trilogy. The Neimoidians were originally envisioned as organic versions of the B1-series battle droids, but such complex and fantastic design was ultimately simplified with the decision to portray the characters with actors wearing animatronic masks rather than through CGI.

The head design of the Geonosians was taken from unused original concept art for the Neimoidians before it was decided that they would be played by actors wearing masks.