Chief science officer
The chief science officer, often simply called the science officer, was the senior staff member aboard a starship or starbase with the broad responsibility of coordinating the sciences division of the post. ()

Duties 
Science officer was a standard position aboard space vessels. Starfleet, Arkonian, Klingon, Romulan, and Vulcan vessels all operated with science officers. (; ; ; ) In the Vulcan High Command, the science officer was assisted by a deputy science officer. () In Starfleet, several junior science officers assisted the science officer. ()

The science officer's primary responsibility was analyzing, observing and theorizing explanations for strange or seemingly unexplainable circumstances in such a way as to provide answers. () Then supply the commanding officer with all reports, observations, and speculations that might have affected the safety of their vessel. ()

When it came to the matter of explaining procreation to the Vaalians, Captain Kirk passed the responsibility of providing an explanation to Spock, citing that "You're the science officer. Why don't you explain it to the young lady." ()

Additional duties included:
 In a medical emergency, the findings of the science officer were heavily relied upon. ()
 Required to keep sufficient data, "all the time". ()
 General survey party required the direction of a science officer. ()
 According to Jadzia Dax, it was a science officer's job to always have a "better idea." ()

Science officers 
In 2268, Harry Mudd observed that Spock "may be a wonderful science officer, but believe me, you couldn't sell fake patents to your mother." ()

In 2270, James T. Kirk considered Commander Spock to be the best science officer in Starfleet. () 

In 2285, Commander Pavel Chekov assumed the position of acting science officer aboard the  following the death of Spock. ()

When Admiral Gregory Quinn wished to show Commander William T. Riker the parasitic being he had brought aboard the  in 2364, Riker told him that he wished to summon his science officer. Quinn then grabbed Riker by the arm and told him that it wouldn't like his science officer, and proceed to attack the commander. ()

When Captain Jean-Luc Picard spoke of the mission he had to complete at the Epsilon Pulsar Cluster to Katherine Pulaski, instead of attending to his own medical needs, Pulasksi was quick to point out that the mission was an "astronomical survey to be conducted by the science officers, I believe." ()

In 2368, Jean-Luc Picard honorably made Jay Gordon Graas an acting science officer during a ship-wide emergency. () 

When Kieran MacDuff attempted to gain the allegiance of Worf, explaining that they were not like the others on the ship. He noted that the "Enterprise had science officers, medical specialists, engineers. Our captain is undoubtedly an accomplished diplomat. But we, we are the warriors." ()

The Romulan officer Parem referred to Geordi La Forge as "the science officer." ()

In 2370, acting Captain Beverly Crusher requested that Ensign Taitt stay on because she needed a science officer at the aft science station. ()

List of science officers
  – 2375 ()
  – , 2257 ()
 Chu'lak – Deep Space 9, 2375 ()
 
 Deep Space 9, 2369 – 2374, chief science officer ()
 , 2371 (illusion) ()
 , 2373 ()
  – , 2270s ()
  – , 2365 – 2366 ()
 Icheb – , 2386 ()
  – , 2372 (
 Kustanovich – , 2350s ()
  – , 2360s ()
  – USS Enterprise, 2250s 
 Mara – , 2268 ()
 Masada – , 2267 ()
 Mirok – Romulan science ship, 2368 ()
 Saru – , 2240s – 2256 ()
 Sonak – USS Enterprise, 2270s ()
 Spock – USS Enterprise, 2250s – 2270; 2270s (; )
  (alternate reality) – , 2258 – , 2260s (; )
  – , 2256 ()
  – USS Enterprise-D, 2364 ()
 Syvar – 2372 ()
 Taitt – USS Enterprise-D, 2370 ()
 T'Pol – , 2151 – 2161 ()
 Tuvok – , 2293, junior science officer (; )
  – , 2293, junior science officer  (; )
  – Deep Space 9, 2372-2375 ()
  – , 2371 ()

See also
 Chief scientist
 Scientific advisor
de:Wissenschaftsoffizier
ja:科学士官
nl:Wetenschappelijke officier
Scientific occupations
Titles