Piccadilly is a major London street, running from Hyde Park Corner in the west to Piccadilly Circus in the east. It is completely within the city of Westminster. The street is part of the A4 road, London's second most important western artery. St. James's lies to the south of the eastern section of the street, while the western section is built up only on the northern side and overlooks Green Park. The area to the north is Mayfair.
It is the location of Fortnum & Mason, the Royal Academy, The Ritz Hotel and Hatchards book shop. Simpsons, once amongst the United Kingdom's leading clothing stores, opened on Piccadilly in the 1930s. The store closed in 1999 and the site is now the flagship shop of the booksellers Waterstone's.
After the Restoration of the English monarchy in 1660, Piccadilly and the area to the north (Mayfair) began to be systematically developed as a fashionable residential locality. Some of the grandest mansions in London were built on the northern side of Piccadilly. Clarendon House (now the location of Albemarle Street), Berkeley House (later Devonshire House), and Sir John Denham's house (later Burlington House) were constructed in the 17th century. Later mansions included Melbourne House (now The Albany), Apsley House, Bath House and Cambridge House. Several members of the Rothschild family had mansions at the western end of the street, and that part of it was colloquially referred to as Rothschild Row. By the 1920s most of these buildings had been demolished or were in institutional use.
21st century Piccadilly has a hybrid range of uses. Despite the presence of two or three famous shops, it is not really one of London's principal shopping streets. The Ritz Hotel is in the street, along with some other luxury hotels. There are also some offices and some very expensive flats. Piccadilly is one of the widest and straightest streets in central London, and is thus popular with motorists.
In the Lord Peter Wimsey novels by Dorothy L. Sayers, Lord Peter's address in London is 110a Piccadilly. The number 110a was chosen in homage to Sir Arthur Conan Doyle's use of 221b Baker Street for Sherlock Holmes.
Selected adjoining streets include: