Chaldeans are members of an autonomous Catholic Church that retains a unique liturgy and tradition while recognising the Pope's authority.
Chaldeans form the majority - about 550,000 - of Iraq's estimated 700,000 Christians.
Their spiritual leader, Chaldean Patriarch Emmanuel III Delly, is based in Baghdad. He was made a cardinal by Pope Benedict XVI in 2007.
His Church originally comprised members of the Nestorian Church, and has had a presence in the country now known as Iraq since the 2nd Century.
Members of the Nestorian Church believe that Jesus Christ has two natures - that of a divine being, the Son of a God, and that of a mortal human.
The Eastern-rite Church the Chaldeans belong to has a traditional liturgical language, Syriac - a linguistic descendant of Aramaic, the language thought by most scholars to have been spoken by Jesus and his disciples.
There are an estimated 50,000 Christians in Mosul, Iraq's third largest city.
While traditionally ethnically and religiously diverse, Mosul is also a centre of the country's oil industry.
A rise in religiously-motivated attacks since the US-led invasion in 2003 has prompted many Christians to leave Iraq.
A number of Christian clergy have been kidnapped or killed by Sunni extremist groups, and several religious institutions have been targeted by bombings.
Estimates suggest as many as 60,000 Christians have fled the country.
Archbishop Paulos Faraj Rahho was abducted after he left Mass in Mosul on 29 February. His body was found two weeks later near Mosul.
Little more than six months earlier, a Chaldean priest and three subdeacons were gunned down outside the same Mosul church.
In January, bombs exploded outside two Chaldean churches, an Assyrian church and a monastery in Mosul, wounding four people.
Perhaps the best known Iraqi Chaldean is Saddam Hussein's former deputy prime minister, Tariq Aziz.