A first officer, also known as an executive officer or XO, was the officer second-in-command of an establishment or unit, ranking right below the commanding officer. In Starfleet, the first officer normally held the rank of lieutenant commander or commander.
Duties a Starfleet first officer might be expected to perform include:
- Advising the commanding officer
- Implementing the commanding officer's orders
- Preparing and issuing duty rosters
- Commanding the starship, starbase or other establishment in the commanding officer's absence or inability to do so
- Evaluating crewmembers aboard the starship, starbase or other establishment with the chief medical officer's and / or counselor's assistance.
Notable first officers
- Vanessa Biondo
- Patricia Graves
- John Greene
- Penelope Koh
- Anne Lansing
- Rafe Mahler
- Elizabeth Singh