Karbala is a city in Iraq

Iraq

Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....

, located about 100 km (62.1 mi) southwest of Baghdad

Baghdad

Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...

. Karbala is the capital of Karbala Governorate, and has an estimated population of 572,300 people (2003).

The city, best known as the location of the Battle of Karbala

Battle of Karbala

The Battle of Karbala took place on Muharram 10, in the year 61 of the Islamic calendar in Karbala, in present day Iraq. On one side of the highly uneven battle were a small group of supporters and relatives of Muhammad's grandson Husain ibn Ali, and on the other was a large military detachment...

 (680), is amongst the holiest cities for Shī‘ah Muslims after Makkah

Mecca

Mecca is a city in the Hijaz and the capital of Makkah province in Saudi Arabia. The city is located inland from Jeddah in a narrow valley at a height of above sea level...

, Madinah

Medina

Medina , or ; also transliterated as Madinah, or madinat al-nabi "the city of the prophet") is a city in the Hejaz region of western Saudi Arabia, and serves as the capital of the Al Madinah Province. It is the second holiest city in Islam, and the burial place of the Islamic Prophet Muhammad, and...

, and Najaf

Najaf

Najaf is a city in Iraq about 160 km south of Baghdad. Its estimated population in 2008 is 560,000 people. It is the capital of Najaf Governorate...

. The city contains the Imam Husayn Shrine

Imam Husayn Shrine

The Shrine of Husayn ibn ‘Alī is one of the oldest mosques on Earth and a holy site of Shīah Islām in the city of Karbalā, Iraq. It stands on the site of the grave of Husayn ibn ‘Alī, the second grandson of Muhammad, near the place where he was killed during the Battle of Karbalā in 680 C.E....

 which is considered sacred by Shias, as well as the shrine of his half brother, al-Abbas ibn 'Ali.
There are several theories as to the origin of the name Karbala.