Manchester Arena bombing

On the night of 22 May 2017, Salman Abedi, a 22-year-old British man of Libyan descent, detonated an improvised explosive device containing triacetone triperoxide (TATP) packed with nuts and bolts in the City Room, a foyer area of Manchester Arena, as attendees were leaving a concert by American singer Ariana Grande. The blast, at 22:31, killed Abedi and 22 concert-goers and family members waiting to collect children from the show. Injury figures were revised upward over subsequent years, reaching 1,017 people recorded as injured by the time of the 2020 public inquiry update, with a 2019 study identifying 239 of these as physical injuries. The dead ranged in age from an eight-year-old girl to a 51-year-old woman, and included two UK-based Polish nationals among mostly British victims.

CCTV evidence showed Abedi conducting reconnaissance of the arena's City Room on multiple occasions in the days before the attack, and members of the public and security staff noticed him behaving suspiciously on the night itself, including one man who directly questioned him about his backpack. Police, security contractor Showsec, and British Transport Police officers did not intervene before the detonation; an official inquiry later found "a number of missed opportunities" and concluded "more should have been done" by police and private security to prevent the bombing. The Islamic State claimed responsibility for the attack via Telegram the following day, though US officials noted the group frequently makes such claims and could not confirm involvement, and inaccuracies in the statement raised doubts about direct coordination.

The investigation initially treated the attack as the work of a wider network, arresting 22 people, but all were released without charge by 11 June 2017 after police concluded Abedi had likely acted alone in sourcing bomb components, although others may have been aware of his plans. Abedi's younger brother, Hashem Abedi, was arrested in Libya on 23 May 2017 and later extradited to the UK, where he was charged on 17 July 2019 with murder, attempted murder and conspiracy to cause an explosion. Following a trial that began 5 February 2020, he was found guilty on 17 March 2020 of 22 counts of murder for helping his brother source bomb-making materials and assisting in constructing the device. On 20 August 2020, he was sentenced to life imprisonment with a minimum term of 55 years, the longest minimum term ever imposed by a British court; the judge noted sentencing rules prevented a whole life order because Abedi was 20 at the time of the offence.

A parliamentary Intelligence and Security Committee report published 22 November 2018 found that MI5 had acted "too slowly" in its handling of intelligence on Salman Abedi, concluding that failings may have caused missed opportunities to prevent the attack, though it could not say the attack would definitely have been stopped. A separate public inquiry, launched in September 2020 and concluding 8 June 2023, produced multiple reports examining arena security and the emergency response, and a coroner ruled in October 2023 that Abedi's death was suicide committed while undertaking a terror attack. An earlier independent review, the Kerslake Report (March 2018), found arena security had been insufficient and criticised delays in the fire service's response and failures of an emergency helpline platform.

In the aftermath, Ariana Grande organized the benefit concert One Love Manchester on 4 June 2017, raising funds for victims, and was later made an honorary citizen of Manchester. Legislative changes named Martyn's Law, after victim Martyn Hett, were later proposed to strengthen venue security requirements.