A Nacelle was an outboard structure found on warp capable vessels.

They contain a number of field coils which create a warp field when injected with highly energetic warp plasma. The warp nacelle is connected to the warp core via plasma transfer conduits, which transferred the plasma in the core to the nacelles.

Nacelles were separated from the ship by large pylons, and usually housed a Bussard ramscoop at the fore end, primarily used for collecting hydrogen from space, especially on Federation starships. Some Some starship classes, possessed nacelles that were integrated into the ship's main structure without pylons. Most Starfleet vessels had two nacelles, however it was possible for ships to have three, four or just one as well.