Ossulstone is an obsolete subdivision (hundred) covering 26.4% of – and the most metropolitan part – of the historic county of Middlesex, England.

[5] Originally meeting at Oswald's Stone, the hundred court eventually moved south-east to the vicinity of Holborn, where by the 19th century it was being held in a building in the north east corner of Red Lion Square, by that stage an outpost of the legal quarter of London close to Lincoln's Inn.

[6] Following the de facto end of hundreds as a judicial unit in the late 19th century, the building became the headquarters of Conway Hall Ethical Society.

Beyond the tidal Thames lay the Blackheath Hundred of Kent to the southeast and those of Lambeth, Brixton and Kingston in Surrey.

[8] Westminster for many purposes formed a "liberty", meaning it enjoyed its own customs as to markets, and freedoms from wider royal precepts and hundred courts.