Caroline Webster Schermerhorn Astor (September 22, 1830–October 30, 1908) preferred to be known simply as Mrs. Astor, which after 1887 was all she had printed on her visiting cards. She was the wife of railroad millionaire William Backhouse Astor Jr.

Her desire to be unchallenged chatelaine of American high society, at least in Newport and New York, was aided by the social climber Ward McAllister , who invented the conceit that there were 400 people who really mattered in society, that being the capacity of Mrs. Astor's ballroom. (McAllister, her distant cousin, referred to her as the "Mystic Rose.") That her husband didn't care for the social whirl did not deflect her one iota and she spent years freezing out people she considered her social inferior. In 1883, however, she was reluctantly moved to admit Alva Vanderbilt, the first wife of William Kissam Vanderbilt, to her social circle after Alva threatened to block the Astors' daughter from participating in a much-awaited costume ball. The blackmail worked.

On the death of her brother-in-law John Jacob Astor III in 1890, his son William Waldorf Astor (1848-1919) attempted to challenge Caroline's right to be the one "Mrs. Astor" and insist that he was now the head of the family. He demanded that his aunt become "Mrs. William Astor" and his wife be known as the "Mrs. Astor." It didn't work. That September, William Waldorf Astor and his wife emigrated to Great Britain, where he later became a viscount.

In retaliation for his aunt's intransigence, William Waldorf Astor then had his father's house, 350 Fifth Avenue, torn down and replaced by the first Waldorf Hotel. Caroline, not willing to live next to a hotel, moved uptown to an opulent mansion at 840 Fifth Avenue. (Her son John Jacob Astor IV built the Astoria hotel at 340 and the two later merged before moving to the present location of the Waldorf=Astoria Hotel).

By the time she moved to the new house her husband had died; she died there herself at age 78 and was interred in the Trinity Church Cemetery in Manhattan.