(covers information from an alternate timeline)
Captain Thomas Halloway was commander of the USS Enterprise-D in an alternate timeline seen by Jean-Luc Picard, created when Q allowed him to prevent a fight with several Nausicaans in 2327 which led to the implantation of an artificial heart.
In the 2369 of that timeline, a confused Picard had asked Worf what his position was. Upon being told he was a lieutenant junior grade assistant astrophysics officer, Picard then inquired who the captain was and was told by Data that Enterprise's captain was Thomas Halloway. (TNG: "Tapestry")
|Commanding officers of the starships Enterprise|
|Enterprise NX-01:||Archer • T'Pol • Tucker • Lorian|
|USS Enterprise:||April • Pike • Kirk • Decker • Spock|
|USS Enterprise-D:||Picard • Riker • Jellico • Halloway|
|ISS Enterprise NX-01:||Forrest|
|ISS Enterprise NCC-1701:||Pike • Kirk|
|USS Enterprise:||Pike • Kirk|
This character was only mentioned in dialogue.
The validity of events during this episode is vague and it is not certain if Q actually allowed Picard to change the past, or if it was merely a hallucination caused by Picard's injuries. Therefore, Halloway may or may not actually exist. Halloway was never actually seen, and for a time the "Tapestry" writers considered referring to Edward Jellico as the Enterprise captain in the altered future. (Star Trek: The Next Generation Companion (2nd ed., p. 236))
In The Lost Era novel The Buried Age, Halloway was assigned as commander of the Enterprise even in the "proper" timeline, but retired shortly before its launch, leaving Picard to accept the assignment in his stead. However, the novel also establishes that Picard's choices of Deanna Troi, Data and Geordi La Forge for their respective positions in his crew were made based on his personal encounters with them in the months and years prior to his taking command of the Enterprise. This, in addition to his reason for choosing William T. Riker as first officer, made it highly unlikely that they would all hold identical positions on an Enterprise commanded by Halloway, without Q's temporal machinations. But Q did state in "Tapestry" that nobody's history other than Picard's would be altered in any way.
Halloway reappears in the short story collection The Sky's the Limit, where it is revealed that he oversaw the construction of the Enterprise but refused to command the ship on its voyages, in order to stay with his wife, Solveig. His full name is given as Thomas Bhupender Halloway. He has two children, Matti and Rupa.
A further story in the collection revealed that Halloway was killed at the battle of Wolf 359, when he commanded the USS Melbourne, having been overseeing its construction at Utopia Planitia at the time of the Borg attack.