- "The name's Sherlock Holmes, and the address is 221B Baker Street. *wink*"
- ―Sherlock Holmes to John Watson.
221B Baker Street is a flat owned by Mrs Hudson who rents it out to Sherlock Holmes and Dr. John Watson. The pair move into the flat together after only having known each other for a short period of time.
The flat is upstairs from Mrs Hudson's, and below 221C Baker Street, which is not rented out throughout the show.
The first room is a large sitting room, complete with fireplace and mantelpiece with several objects on it, including a Persian slipper, in which Sherlock puts his tobacco, and a skull. In the room is also a table where Sherlock keeps his famous deerstalker, and two chairs. There is a desk where Holmes writes, and beside it is a doorway that leads to his bedroom. This room doubles as the reception for their clients.
Sherlock also practices shooting his pistol in this room. Painted on the wall is a yellow smiley face, decorated with bullet shots.
The kitchen, connected to the sitting room, also holds the dining table, which is usually covered with various scientific instruments. When not at St. Bartholomew's Hospital, Sherlock uses this room to conduct experiments.
Holmes has a bedroom with green walls, a medium-sized bed, a bedside table, and a dressing table and storage cabinet. John's bedroom – an incredibly organised room as a remnant from his time in the military – is located upstairs.
After meeting with Irene Adler, three American agents break into Baker Street and tried to find her camera phone. Mrs Hudson rescued it by bursting into fake tears. Sherlock contacted Detective Greg Lestrade, explaining the situation, and added on that he needed an ambulance because the agent had fallen out of the window. He proceeded to throw the agent out of the window and onto Mrs Hudson's bins a number of times.
List of objects that can be found at 221B
- Skull (declared as a "friend" of Sherlock's)
- Union Jack cushion
- Sudokube 
- Microwave (containing – at one point – a glass full of human eyes)
- Water heater
- Fairy lights
- Music stand
- London A-Z
- Knife (keeps unopened letters in place on the mantlepiece)
- Periodic Table of the elements (in Sherlock's bedroom)
- Box with a prepared bat
- Decorative bison skull with headphones attached
- Cluedo board, stabbed to the wall with a knife
- Both John and Sherlock's computers
- John's pistol
- A small tea table
- John's RAMC mug
- An impressive assortment of laboratory glassware
- Vintage casing of different ammunition
Behind the scenes
The filming location for 221B Baker Street, together with the real-world Speedy's Sandwich Bar, is 187 North Gower Street near Euston Square Underground station in London.
- Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- Thompson, Steve; Moffat, Steven; Gatiss, Mark (writers) & McCarthy, Colm (director). (5 January, 2014). "The Sign of Three". Sherlock (2010). Series 3. Episode 2. BBC One.
- Moffat, Steven (writer) & McGuigan, Paul (director). (1 January, 2012). "A Scandal in Belgravia". Sherlock (2010). Series 2. Episode 1. BBC One.
- Thompson, Steve (writer) & Lyn, Euros (director). (1 August, 2010). "The Blind Banker". Sherlock (2010). Series 1. Episode 2. BBC One.
- All throughout Sherlock (2010)
- "Sherlock Holmes and the riddle of the packed sandwich bar". Daily Mail.