The M-11 Starbase Club was an officers' lounge situated on planet M-11 within a building at Starbase 11 where visitors and staff gathered for banter in the 2260s. An individual would buy drinks and food from the barkeep, and would either stay at the small bar or gravitate toward one of many tables in the facility. In the center of the bar, there was a rectangular sign, with black lettering on a white background, which read "M-11 Starbase Club".
In 2267, Captain James T. Kirk entered this bar with Lieutenant Commander Leonard McCoy. Kirk saw and spoke with many classmates of his, and McCoy met Areel Shaw, an old flame of Kirk's. Additionally, three of the judges who were later present at the captain's court martial were together at one of the lounge's tables, in light conversation.
Much later, Kirk had a conversation with Shaw, during which he learned she was the prosecutor at his court martial, and received a recommendation from her on a lawyer the captain should hire for his defense. (TOS: "Court Martial")