Marsham Street is a street in the City of Westminster in London, England. It is approximately a mile in length and runs south from Great Peter Street, near Victoria Street and Parliament Square. It bisects Horseferry Road and backs on to Smith Square, formerly home to the Conservative Party. Like many streets in the area, it has long been the location to offices of the Government of the United Kingdom and is currently home to the Home Office and the Department for Transport. Along with Great Smith Street to the north, and John Islip Street to the south, it is designated the B326 in the Great Britain road numbering scheme.
Marsham Street has been subject to a number of high end residential developments formed out of what used to be Westminster Hospital and associated former nursing accommodation. These developments were completed in the period 2005-2007 and are now attracting purchasers who traditionally would have sought out accommodation in Chelsea and Knightsbridge but are attracted by high specification buildings and attractive pricing by developers.