An Officers' Club, colloquially known as an "O-Club", is a bar and lounge aboard UNSC vessels, and presumably on many UNSC bases. This is forbidden territory to all crew on board aboard vessels, save those who were commissioned officers.
- The Gettysburg has the only mentioned O-Club. Where it had a massive table of oak, scored with numerous gouges and scorches from a hundred cigars casually set upon its surface. There was a bar stocked with bottles containing a rainbow collection of liquors. It also housed the UNSC gold-fringed blue flag. Along with photos of Past Officers and Captains of the Gettysburg. And a tin Civil War daguerreotypes that displayed the battlefields full of charging men and cavalry and cannons.