The first Romulan commander seen in Star Trek: The Next Generation is Tebok. He appears in “The Neutral Zone,” the first-season finale, when the USS Enterprise-D encounters a Romulan warbird near the Federation–Romulan Neutral Zone.
The episode originally aired on May 16, 1988, and marked the Romulans’ return to TNG after the series had spent most of its first season introducing other threats. Tebok tells Captain Picard that Romulan outposts have also been destroyed and warns that the Romulans are “back” after decades of absence.
Tebok was played by Marc Alaimo, who later became widely known as Gul Dukat on Star Trek: Deep Space Nine. The Romulan officer accompanying him is Subcommander Thei. A common mix-up is Tomalak, another prominent TNG Romulan, but Tomalak first appears later, in the third-season episode “The Enemy.”