While the Klingons may be more vicious and the Borg more terrifying, the Romulans have been one of the most consistent baddies in all of Star Trek. Using deceit and trickery to their advantage, the Romulans have proven on many occasions to be as ruthless as they are intelligent in their dealings with the Federation.
From their first appearance in the original series to their legendary battles in Enterprise, there is no doubt that the Romulans make for great TV. As long as the pointy-eared cousins of the Vulcans continue to bother the Federation, viewers will always have a memorable villain to root against.
Birthright (The Next Generation)
The theme of identity is a large part of the Star Trek mythos, and few characters struggled with their identity quite like Lt. Worf. The episode "Birthright" from The Next Generation saw Worf in search of his biological father after learning that he may still be alive. In his quest, Worf discovers a community of Klingon and Romulan prisoners of war, who all live together in harmony.
Never quite comfortable in the human world or Klingon world, Worf's emotions are doubly tested by the presence of Romulans. Always the mortal enemy of the Klingons, Worf finds that he can't fully trust them, even if they prove to be peaceful. "Birthright" is a fascinating story because it shows another side of Star Trek's most reviled villains.
The Enemy (The Next Generation)
Romulans flourished in The Next Generation, and were one of the most consistent villains to appear in the long running series. The episode "The Enemy" finds Geordie LaForge trapped on a dangerous planet where he must work together with a Romulan soldier in order for them both to survive the ordeal.
Exuding all of the hopefulness that Gene Roddenberry intended, "The Enemy" puts a clever spin on its own name. By forcing two mortal enemies together into cooperation, the episode shows that there is more common ground between them than they may believe. While it may not be considered one of the best episodes of The Next Generation, it is still a shining example of what made the show great.
Face Of The Enemy (The Next Generation)
Even when confronted with difficult odds, the members of the Federation have shown time and again that they will go to any lengths to end hostilities, and save lives. "Face of the Enemy" was one of the most shocking moments of The Next Generation and found Counselor Troi surgically altered to look like a Romulan. Kidnapped in order to play the part of a high ranking official, Troi goes along with the plan to save lives.
Despite its convoluted premise, the episode gave the viewer an inside look a the mysterious world of the Romulans. Troi is featured in one of her best episodes, and the she is able to show off the greatest aspects of her personality when attempting to save the day.
Unification (The Next Generation)
A Romulan episode is usually exciting enough, but the return of one of Star Trek's most beloved characters was an added treat. "Unification" sees the Enterprise follow Ambassador Spock deep into Romulan territory as he embarks on a dangerous mission to bring peace.
Attempting to save the day with his powerful logic, Spock's mission brings him into the world of The Next Generation. "Unification" is a treat for fans because it not only brings back Spock, but also shows off the Romulan home world and gives viewers more backstory on the mystery villains.
Inter Arma Enim Silent Leges (Deep Space Nine)
Usually dealing with other threats, the crew of Deep Space Nine also had a fair amount of run-ins with Romulans as the show progressed. The episode "Inter Arma Enim Silent Leges" features Dr. Bashir traveling to the Romulan home world to attend a medical conference. On the way there, he is recruited by Section 31 to provide medical care to a high-ranking Romulan official.
Featuring all of the aspects that made later seasons DS9 great, the episode has a level of high-stakes intrigue that is missing from other Trek shows. What the episode also does, is further establish the dark tie between the Federation and the Romulan empire, as the Dominion War raged on.
The Defector (The Next Generation)
Showing to always be untrustworthy, many great Romulan episodes play out like mysteries. The episode "The Defector" features a high-ranking Romulan official who uses the Enterprise for asylum as he claims to defect from the empire with news of an imminent invasion attempt.
Unlike some of the most powerful Star Trek aliens that use muscle to get their way, Romulans weave tapestries of deceit. "The Defector" is one of Captain Picard's biggest challenges because it requires him to think logically, while also utilizing his uncanny ability for compassion, even for a former enemy.
The Enterprise Incident (The Original Series)
Despite appearing only a few time in The Original Series, the Romulans made a shockingly strong impression on the audience. In "The Enterprise Incident", a seemingly demented Captain Kirk orders the Enterprise into Romulan space where it is promptly captured. Defying his captain, Spock must find a way to free his crew from the clutches of the enemy.
Further fleshing out what was established earlier in the series, "The Enterprise Incident" added more to the Romulan mythos. Spock gets to be the star of the episode as he must use his logical Vulcan mind to outwit his cousins, the Romulans.
United (Enterprise)
Though it wasn't the most popular series in its time, Star Trek Enterprise was a fun look at the universe before The Original Series. The episode "United" was part of a larger story arc, and saw Captain Archer desperately attempt to convince the Vulcans, Tellarite, and Andorans to team up in order to stop a Romulan chameleon ship.
By allowing the Romulans to live up to their full potential, the three part story arc shows the frightening possibilities of their wrath. While they may be simply the dastardly villain, they work perfectly as a foil to Captain Archer's quest for all things good in the galaxy.
In The Pale Moonlight (Deep Space Nine)
While Star Trek is usually about the best possible future for mankind, Deep Space Nine often showed much darker possibilities. Set at the height of the Dominion War, "In the Pale Moonlight" sees Captain Sisko go to extreme measures to ensure that the Romulans join forces with the Federation/Klingon alliance, even at the risk of his own morals.
Generally considered one of the best ever episodes of DS9, "In the Pale Moonlight" is also one of the darkest. The bleakness of the war has pushed the usually moralistic Captain Sisko to his limits, and that low-point includes lying and deceit. In many ways, the episode shows that there is little difference between humans and Romulans after all.
Balance Of Terror (The Original Series)
As for debuts, the Romulans certainly burst on the scene with a tremendous bang. The episode "Balance of Terror" sees the Enterprise's state of jubilation interrupted by the sudden appearance of a Romulan vessel that is making violent moves towards Federation space.
Locked in a cat-and-mouse battle with the Romulan captain, Kirk is pushed to the limits of his wits by his unscrupulous enemy. The scope of the episode is small but the scale threatens to escalate to galaxy wide war. Though they were just introduced in the episode, the Romulans quickly proved to be a dark mirror to the Federation's enlightened future.