Counselor aboard the U.S.S. Enterprise-D under the command of Captain Jean-Luc Picard.
Daughter of Lwaxana Troi and Ian Andrew Troi, Deanna was betrothed to Wyatt Miller through the Betaoid custom of genetic bonding when they were both children. Deanna and Wyatt never married, though, because Wyatt chose to join the last surviving Tarellians in search of a cure for the Tarellian plauge.
Deanna's father used to read her heroic stories about the ancient American West on planet Earth, and she remained fond of these stories into her adulthood. Troi studied psycology at the University of Betazed prior to her joining Starfleet.
While a psycology student on Betazed, Troi became romantically involved with Lieutenant William T. Riker. Troi had hopes of a serious commitment between the two, but Riker's career plans took him away to an assignment aboard the U.S.S. Potemkin. Troi graduated from the Academy (possibly having taken classes on Betazed) in 2359. Troi was once involuntarily impregnated by an unknown noncorporeal life-form. Troi had named the child Ian Andrew, after her late father.
Troi suffered a brief loss of her empathic powers in 2367 from proximity to a newly discovered group of two-dimensional creatures. Although Troi found the loss disconcerting, she was pleased to discover that she could still function as ship's counselor without her Betazoid abilities. Counselor Troi assummed temporary command of the Enterprise-D on stardate 45156 when the ship was disabled from collision with two quantum filaments. Troi, who held the rank of lieutenant commander, was the senior officer on the bridge at the time. Troi said she never met a chocolate she didn't like.