Final answer:
The most famous room in the White House, used by the President as an office, is called the Green Room.
Step-by-step explanation:
The most famous room in the White House, which was used as an office by President but he never slept there, is called the Green Room.
This room is known for its luxurious furnishings and has been used by many presidents as a formal gathering space. One notable example is when President Barack Obama met with former Secretary of State Hillary Clinton in the Green Room.