Multiple realities
(covers information from several alternate timelines)
Executive officer redirects here; for a business chief executive officer, please see CEO.
"Captain, as your exec, it's my duty to point out alternatives."
– Will Decker to James T. Kirk, 2270s (Star Trek: The Motion Picture)

Aboard a starship the first officer or executive officer (or XO) was the second-in-command, just below the captain.


In Starfleet the position was usually held by an officer with the rank of commander or lieutenant commander.

In Starfleet's early period of existence, the first officer would accompany the captain on landing parties, depending on the situation. By the 24th century, however, it was the first officer who usually led away teams while the captain remained on the ship.

In the 22nd and 23rd centuries, the first officer served as a department head first and the executive officer second (similar to the second officer and third officer) and only took command when the captain left the bridge, as such, there was no first officer's station as there would be in the 24th century, as the XO would alternate between the command chair and their station as a department head.

Noted functions of the first officer aboard a Federation starship were:

Aboard a Klingon warship, the first officer served the Captain, but stood for the crew. They also reviewed and kept the ship's record of battle. (DS9: "Soldiers of the Empire")

Noted first officers

List of first officers


  • Lieutenant Commander Data
    • USS Enterprise-D (2369)
  • Lieutenant Commander Una
    • USS Enterprise (2254)
  • Commander Shelby
    • USS Enterprise-D (2367)
  • Lieutenant / Lieutenant Commander Worf
    • USS Enterprise-D (2370)
    • USS Defiant (2372–2375)
    • USS Sao Paulo (2375)
A deleted scene from Star Trek Nemesis introduced Commander Martin Madden as the new first officer of the USS Enterprise-E

Klingon Empire

  • Commander Kurn
    • USS Enterprise-D (2366, part of the Officer Exchange Program)


Mirror universe

Alternate timelines

  • Lieutenant Sato
    • Enterprise NX-01 (2165)
  • Commander Thelin
    • USS Enterprise (2269)
  • Commander Worf
    • USS Enterprise-D (2367 – 2370)
This chart shows only general equivalencies based on the ranks used by many governments on Earth, as well as the rest of the galaxy.



  • Commander Worf
    • USS Enterprise-E (2380)

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