Margaret "Daisy" Van Alen Bruguière (née Post; July 15, 1876 – January 20, 1969) was an American socialite, art collector and the niece of Frederick Vanderbilt.

[3] She spent her summers at the Post family's residence in Newport, 'Rosetta', and winters at her uncle Frederick Vanderbilt's Hudson Valley estate, Hyde Park.

[1] She gave $10,000 for the landscaping and renaming of Washington Square Park in Newport in honor of her friend, President Dwight D.

[4] She was also a prominent support of the Republican Party, and was known for hosting political fundraisers at her various homes in Newport and Washington.

[1] By the 1960s, many of Newport's grand mansions that lined Bellevue Avenue had been turned into public museums or schools.

[6] She later donated the estate as a public park and museum, today known as the Vanderbilt Mansion National Historic Site.