First officer

A First officer (aka Executive officer, XO, and Number One) is the second-highest ranking officer aboard a starship or space station, usually a Commander or Lieutenant Commander. He or she takes command if the commanding officer is unable to. If the first officer is also unable to take command, the second officer is in charge.

First officers by name

 * Commander Quint Freedman of the USS Incursion (2377)
 * Lieutenant Commander George Samuel Kirk Sr. of the USS Enterprise (NCC-1701) (2243)
 * Commander William T. Riker of the USS Enterprise-D;
 * Commander Elizabeth Shelby of the USS Excalibur (NCC-26517) (2368-2376)
 * Commander Shundresh of the USS Enterprise (NCC-1701) (2245-2251)
 * Commander Spock of the USS Enterprise (NCC-1701) (2264-2281)
 * Captain Spock of the USS Enterprise (NCC-1701-A) (2286-2293)
 * Commander Gilaad Ben Zoma of the USS Stargazer
 * Commander Christine Vale of the USS Titan
 * Commander Dakona Raal of the USS Orion

First officers by post

 * USS Enterprise (NCC-1701)
 * Lieutenant Commander George Samuel Kirk Sr. (2243, MIA)
 * Commander Shundresh (2245-2251)
 * Commander Spock (2264-2281)
 * USS Enterprise (NCC-1701-A): Captain Spock (2286-2293)
 * USS Excalibur (NCC-26517): Commander Elizabeth Shelby (2368-2376)
 * USS Incursion: Commander Quint Freedman (2377)
 * USS Stargazer: Commander Gilaad Ben Zoma (2333-2355)
 * USS Titan: Commander Christine Vale
 * USS Orion Dakona Raal

2243

 * Lieutenant George Samuel Kirk Sr. of the USS Enterprise (NCC-1701)

2245

 * Commander Shundresh of the USS Enterprise (NCC-1701)

2264

 * Lieutenant Commander Spock of the USS Enterprise (NCC-1701)

2286

 * Captain Spock of the USS Enterprise (NCC-1701-A)

2333

 * Commander Gilaad Ben Zoma of the USS Stargazer

2364

 * Commander William T. Riker of the USS Enterprise (NCC-1701-D)

2367

 * Commander Elizabeth Shelby of the USS Chekov

2368

 * Commander Elizabeth Shelby of the USS Excalibur (NCC-26517)

2369

 * Major Kira Nerys of Deep Space Nine

2372

 * Commander William T. Riker of the USS Enterprise (NCC-1701-E)

2376

 * Commander Dakona Raal of the USS Orion

2377

 * Commander Quint Freedman of the USS Incursion

2379

 * Commander Christine Vale of the USS Titan

2380

 * Commander Worf of the USS Enterprise (NCC-1701-E)