Harriett Low Hillard (18 May 1809 – 1877) was an American woman of letters and diarist.
From 1829 to 1833 she lived in the Portuguese colony of Macau on the South China coast and she and her sickly aunt became the first American women to go to China.
During her stay from 1829 to 1833, she wrote a journal in the form of letters to her older sister Molly (Mary Ann, 1808–1851), and became acquainted with many of the influential individuals in the colony.
After her return to the United States, she married and moved to London, returning to New York with her husband and five daughters in 1848.
Her journal is now part of the Low-Mills collection in the Library of Congress.