A suicide bomber attacked a Shia procession commemorating the day of Ashura in Karachi, Pakistan, causing 43 deaths.

The 2009 Karachi bombing or Ashura attack took place on 28 December 2009 inside a Shia procession commemorating the day of Ashura, at Muhammad Ali Jinnah Road, Karachi, Pakistan. Ashura is the holiest of days for followers of Shia Islam and marks the anniversary of the death of Imam Hussain, grandson of the Islamic prophet Muhammad, who was killed at the Battle of Karbala in 680. At least 30 people were initially reported to have been killed, later figures revealed even more deaths while dozens were left injured in the wake of the attack. The attacker marched amongst the procession with tens of thousands of people attending the march. There is some speculation amongst officials as to whether the nature of the blast was that of a suicide attack or a remotely detonated or planted bomb.

Shia Islam is the second-largest branch of Islam. It holds that Muhammad designated Ali ibn Abi Talib as both his political successor (caliph) and as the spiritual leader of the Muslim community (imam). However, his right is understood to have been usurped by a number of Muhammad's companions at the meeting of Saqifa, during which they appointed Abu Bakr as caliph instead. As such, Sunni Muslims believe Abu Bakr, Umar, Uthman and Ali to be 'rightly-guided caliphs', whereas Shia Muslims regard only Ali as the legitimate successor.

Ashura is a day of commemoration in Islam. It occurs annually on the tenth of Muharram, the first month of the Islamic calendar. For Sunni Muslims, Ashura marks the parting of the Red Sea by Moses and the salvation of the Israelites. Also on this day, it is believed that Noah disembarked from the Ark, God forgave Adam, and Joseph was released from prison, among various other auspicious events having occurred on Ashura according to Sunni tradition. Ashura is celebrated in Sunni Islam through supererogatory fasting and other acceptable expressions of joy. In some Sunni communities, the annual Ashura festivities include carnivals, bonfires, and special dishes, even though some Sunni scholars have criticized such practices.