"A Scandal in Belgravia" is the first episode of the second series of the BBC crime drama series Sherlock, which follows the modern-day adventures of Sherlock Holmes, and was first broadcast by BBC One on 1 January 2012. It was written by co-creator Steven Moffat, and directed by Paul McGuigan. The episode was based on "A Scandal in Bohemia", a short story by Sir Arthur Conan Doyle.

The episode depicts Sherlock Holmes' (Benedict Cumberbatch) confrontation with Irene Adler (Lara Pulver), a dominatrix who has compromising photographs taken with a female member of the royal family. The photographs are stored inside her mobile phone, along with other valuable information which makes her a target of various political factions. Sherlock spends much of the episode keeping the device out of enemy hands while trying to deduce its password. Besides referring to the Doyle short story, the episode title names Belgravia, a district of London adjacent to the grounds of Buckingham Palace.

After its broadcast on BBC One, the episode was given consolidated figures of 10.663 million viewers in the United Kingdom. Critical reactions toward the episode were largely positive, with reviewers praising the writing, acting and direction. The episode sparked controversy for showing the character of Irene Adler in the nude; carefully using camera angles to avoid exposing private areas, pre-watershed.

The series follows a contemporary update of Sir Arthur Conan Doyle's Sherlock Holmes detective stories. Throughout the first series, it is revealed that a man named Moriarty, a "consulting criminal", was to some extent responsible for orchestrating the crimes throughout the three episodes. In the series finale, "The Great Game", Sherlock (Benedict Cumberbatch) and John Watson (Martin Freeman) come face to face with Jim Moriarty (Andrew Scott), who has snipers targeting them. Moriarty intends to have the two killed, but in the closing scenes, Sherlock aims a handgun at an explosive vest, threatening to shoot it.

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