The I.S.S. O'Brien is an Odyssey-class Dreadnought and a flagship of the Terran Empire's invasion forces during their second invasion of the prime universe. The O'Brien is equipped with technology to create and maintain trans-dimensional portals, possibly based on information gleaned from the Orb of Possibilities.
- “Mirror Universe Incursion”: The O'Brien is the command ship of the Terran fleet invading the prime universe and attacking Vauthil Station.
- The O'Brien is likely named after either Miles "Smiley" O'Brien or his son James.
- The O'Brien is one of several possible dreadnoughts that may lead the final wave of Imperial ships.