Park Street is a street in Mayfair, London, England. It is the longest street on the Grosvenor Estate. It is a one-way street running south to north from a t-junction with South Street to a crossroads with Oxford Street, where it continues north as Portman Street. It was formerly known as Hyde Park Street. House building on the street began in the late 1720s, and was completed in the late 1770s, and the only surviving original properties are nos 70 to 78.