Baron Hillingdon, of Hillingdon in the County of Middlesex, was a title in the Peerage of the United Kingdom held by the Mills family. This family descended from Charles Mills, a Director of the Honourable East India Company and a member of the Council of India. On 17 November 1868 he was created a Baronet in the Baronetage of the United Kingdom. He was succeeded by his only son, the second Baronet. He was a banker and Conservative politician. On 15 February 1886 he was raised to the Peerage of the United Kingdom as Baron Hillingdon, of Hillingdon in the County of Middlesex. When he died the titles passed to his eldest son, the second Baron. He was also a banker and Conservative politician. He was succeeded by his son, the third Baron. He sat as Conservative Member of Parliament for Uxbridge. When he died the titles passed to his eldest son, the fourth Baron. He died without surviving male issue and was succeeded by his kinsman, the fifth Baronet. On his death in 1982 the titles became extinct.
Hillingdon Court, built by Sir Charles Mills, 1st Baronet in 1858, served as the Mills family home.