Mrs. Hudson is the landlady of 221B Baker Street, the London residence where Sherlock Holmes and Dr. Watson live in many of the stories. In the short story "The Adventure of the Naval Treaty," Holmes says "Her cuisine is a little limited, but she has as good an idea of breakfast as a Scotchwoman,"^[3] which some readers have taken to mean that she is Scottish, and others that she cannot possibly be. Other than one mention of her "stately tread" in the novel A Study in Scarlet, she is given no physical description or first name, although some commentators have identified her with the "Martha" in "His Last Bow".^[4][5]

In the first Sherlock Holmes story, A Study in Scarlet, there is a landlady of 221B Baker Street, though her name is not given. The landlady is identified as Mrs. Hudson in the following story, The Sign of the Four.^[1] At one point in "A Scandal in Bohemia" Holmes calls the landlady "Mrs. Turner", rather than Mrs. Hudson, which has caused much speculation among Holmes fans.^[6] It has been suggested that Mrs. Turner was substituting for Mrs. Hudson or that Holmes or Watson mistakenly used the wrong name, though it may have simply been an error by Doyle, since the name Mrs. Turner also appeared in an early draft of "The Adventure of the Empty House" but was corrected to Mrs. Hudson.^[7] When Holmes is in retirement in Sussex in "The Adventure of the Lion's Mane", he says he is living with his "old housekeeper", which some readers believe is Mrs. Hudson.^[1]

Holmes tells Watson in "The Adventure of the Empty House" that his sudden return to Baker Street three years after his supposed death "threw Mrs. Hudson into violent hysterics". In the same story, Watson notes that their old Baker Street rooms are unchanged due to "the supervision of Mycroft Holmes and the immediate care of Mrs. Hudson".^[8] Mrs. Hudson also places herself in danger to assist Holmes in the story, by carefully moving a bust of Holmes every quarter of an hour to fool a sniper, Colonel Sebastian Moran, into thinking the bust is actually Holmes.^[9] When Moran fires his gun, the bullet passes through the bust and hits the wall, after which it is picked up by Mrs. Hudson. She expresses dismay that the bust of Holmes was spoiled by the bullet and presents the bullet to Holmes.^[8]

There is no mention in the stories of Mrs. Hudson's husband. It has been suggested as a possibility that she was never married, since the title "Mrs." was used in the Victorian era as a respectful title for high-ranking domestic staff, regardless of marital status.^[5] While no relatives of Mrs. Hudson's are identified in the stories, she shares her surname with a character in "The Adventure of the Gloria Scott" and another in "The Adventure of the Six Napoleons". There are also characters with the surname Turner, a name which may or may not be connected with Mrs. Hudson in "A Scandal in Bohemia", in "The Boscombe Valley Mystery".^[1]

Daniel Smith writes in his book The Sherlock Holmes Companion that, though few details are given about Mrs. Hudson in Doyle's stories, the character "has become one of the iconic figures of Sherlock Holmes's world" due largely to portrayals of Mrs. Hudson in film and television.^[2]