Ossulstone is an obsolete subdivision (hundred) covering 26.4% of – and the most metropolitan part – of the historic county of Middlesex, England. It surrounded but did not include the City of London and the area has been entirely absorbed by the growth of London. It now corresponds to the seven London Boroughs of Inner London north of the Thames and, from Outer London, in decreasing order, certain historic parishes of the London boroughs of Ealing, Brent, Barnet, and Haringey.