Christianity is the largest religion in Ethiopia, Eritrea, among Ethiopians, Eritreans, the Habesha Community and their diaspora. Christianity in these countries and communities, dates back to the ancient African (East African-Horn African) Kingdom of Aksum, when King Ezana first converted to the faith and later on became the official religion of his kingdom and the Ethiopian Empire. Eastern Christianity is the main Christian cultural tradition of these countries and communities.

There are several different branches of Christianity in the Ethiopian and Eritrean communities, and can be broken down into several denominations. The largest and oldest branch of Christianity in Ethiopia and Eritrea are the Orthodox Tewahedo churches, a group of culturally and theologically related Oriental Orthodox churches. The second largest Christian branch in Ethiopia and Eritrea is P'ent'ay (Ethiopian-Eritrean Evangelicalism), a grouping of several Evangelical Protestant denominations. The third branch of Christianity in the region is the Catholic Church or Catholicism.

Orthodox Tewahedo 

Orthodox Tewahedo is the common and historical name of the Oriental Orthodox church in the former Ethiopian Empire, that would later become the Ethiopian Orthodox Tewahedo Church, the Eritrean Orthodox Tewahedo Church, and the most dominant Christian denominations in its successor states of Ethiopia and Eritrea respectively. It is one of the few pre-colonial Christian churches in Sub-Saharan Africa and one of the oldest Christian churches in the world with Ethiopia (then including Eritrea) being historically the second country, following only Armenia, to have officially proclaimed Christianity as its state religion (in AD 333). The Ethiopian Orthodox Tewahedo Church (, Yäityop'ya ortodoks täwahedo bétäkrestyan) and the Eritrean Orthodox Tewahedo Church (Tigrinya: ቤተ ክርስትያን ተዋህዶ ኤርትራ, Tewahədo Bet'ə K'rstian Ertra) are in communion with the the Coptic Orthodox Church of Alexandria, the Malankara Orthodox Syrian Church, the Armenian Apostolic Church and the Syriac Orthodox Church. 

The Ethiopian Orthodox Tewahedo Church is the largest of the Oriental Orthodox Christian churches and has a membership of about 36 million people, the majority of whom live in Ethiopia. It is also a founding member of the World Council of Churches.

From the first half of the 4th century until 1959, the Orthodox Tewahedo churches were administratively part of the Coptic Orthodox Church of Alexandria   it was granted autocephaly with its own patriarch by Saint Pope Cyril VI of Alexandria, Pope of the Coptic Orthodox Church of Alexandria. Following the independence of Eritrea from Ethiopia in 1993, the Eritrean Orthodox Tewahedo Church was made autocephalous by Pope Shenouda III of Alexandria and it officially separated from what was now to become the Ethiopian Orthodox Tewahedo Church.

P'ent'ay - Ethiopian-Eritrean Evangelicalism 

P'ent'ay (from Ge'ez: ጴንጤ), also known as Ethiopian–Eritrean Evangelicalism, is a term for Evangelical Christians and other Eastern/Oriental-oriented Protestants within Ethiopia and Eritrea, and the Ethiopian and Eritrean diaspora abroad. Prominent movements among them have been Pentecostalism, the Baptist tradition, Lutheranism, and the Mennonite-Anabaptist tradition. The denominations and organizations in Ethiopian and Eritrean societies are also collectively known as Ethiopian–Eritrean Evangelicalism, the Ethiopian–Eritrean Evangelical Church, or Wenigēlawī (from Ge'ez: ወንጌላዊ) which directly translates to “Evangelical.”

Ethiopian and Eritrean Protestant Christians are the result of American and European Protestant missionary work among youth who left the Orthodox Tewahedo churches because of theological differences, and later fanned by persecution against them. P'ent'ay Christians schismed from the Orthodox Tewahedo churches, other branches of Christianity, or converted from other religions with the aid of Protestant missionaries to reform Ethiopian Christianity and Eritrean Christianity from what they perceived as doctrinal–theological diversions. Since the creation of P'ent'ay churches and organisations.

Denominations 
The major Protestant denominations in Ethiopia and Eritrea are a group of indigenous, closely linked (part of the  or community of churches) full communion interdenominational ecumenical group of Baptist, Lutheran, Pentecostal, and Mennonite denominations.

Primary denominations 

 The Ethiopian Kale Heywet (Word of Life) Church, a charismatic Evangelical Protestant denomination with Pentecostal, Baptist, and Mennonite roots. It is associated with the Sudan Interior Mission, an interdenominational organization, and has an Eritrean branch.
 The Ethiopian Evangelical Church Mekane Yesus (Place of Jesus), a Lutheran denomination which includes a Presbyterian-leaning synod. The Eritrean Evangelical Church Mekane Yesus is the Eritrean Lutheran branch of this Evangelical Protestant denomination. The Ethiopian Lutheran denomination is the largest non-united Lutheran Christian denomination (see list of Christian denominations by number of members).
 The Evangelical Lutheran Church of Eritrea, a Lutheran denomination which joined the Lutheran World Federation in 1963.
 The Ethiopian Full Gospel Believers' Church, a Pentecostal denomination with Mennonite influence.
 The Meserete Kristos (Christ Foundation) Church, a Mennonite denomination with Pentecostal influence.

Some P'ent'ay communities—especially the Mekane Yesus Lutheran Church for example—have been influenced by the Orthodox Tewahedo churches, which represents the dominant traditional Ethiopian and Eritrean Christian demographic, but for the most part are very Pentecostal in their worship and theology.

Other denominations 

 Ammanuel Baptist Church
 Christian Brethren
 Misgana Church of Ethiopia
 Assemblies of God –  Pentecostal
 Hiwot Berhan Church (Light of Life Church)
 Emnet Kristos
 Berhane Wongel – Gospel Light
 Ethiopian Addis Kidan Baptist Church
 Evangelical Church of Eritrea
 Lutheran Church of Eritrea
 Middle East General Mission
 Seventh-day Adventist Church
 Anglicanism is represented in Ethiopia and Eritrea by the Episcopal Church in Jerusalem and the Middle East and Episcopal Anglican Province of Alexandria; Ethiopia and Eritrea are both part of the Diocese of Egypt, which also includes other countries in the Horn of Africa as well as the North Africa region. There are two Episcopal churches in Ethiopia, one is in Addis Ababa and the other in Gambela, while in Eritrea there are no officially operated congregations at this time.
 Rema Church
 Hallelujah Church
 Faith Mission
 Faith Church of Christ
 Philadelphia Church
 Presbyterian Evangelical Church
 Trinity Fellowship Church
 Dubre Bethel Church
 Church of the Living God
 New Covenant Church

History 
For the most part, Ethiopian and Eritrean Protestants state that their form of Christianity is both the reformation of the current Orthodox Tewahedo churches as well as the restoration of it to the original Ethiopian Christianity. They believe Ethiopian Orthodox Christianity was paganized after the 960s, during the reign of queen Gudit, who destroyed and burned most of the church's possessions and scriptures. They claim those events have led to the gradual paganization of the Oriental Orthodox Churches which they say is now merely dominated by rituals, hearsay and fables. P'ent'ay Christians use the alleged "secularized teaching" of the current Ethiopian and Eritrean Orthodox churches, the alleged inability of most Orthodox followers to live according to the instructions of the Bible and the deuterocanonical books used by rural priests, as a proof to their belief in the Orthodox Tewahedo teaching is also mainly syncretized. P'ent'ay Christians use the history of the Ethiopian Orthodox Christianity prior to the 1960s as their own history, despite lacking historical continuity.

It was only during the early 20th century that American and European missionaries spread Protestantism with Mennonite and Pentecostal churches through the Sudan Interior Mission (SIM) which led to the formation of the Ethiopian Kale Heywet Church. When the SIM continued its movement after a brief ban during Ethiopia's war with Italy, it is written that the missionaries were taken aback by the fruits of their initial mission. Peter Heyling, a German Lutheran was the first Protestant missionary in Ethiopia, and is regarded as one of the founding fathers of the Lutheran denomination Ethiopian Evangelical Church Mekane Yesus alongside Gudina Tumsa and Emmanuel Abraham. Protestantism has had a presence in Eritrea for over 150 years much of which started when the Swedish Evangelical Mission (SEM) of the Church of Sweden first sent missionaries to preach to the Kunama people in 1866. Between the late-19th and late-20th centuries, the SEM undertook the task of translating the Bible into various Eritrean languages and influenced churches like the Evangelical Lutheran Church of Eritrea. The Eastern Mennonite Missions also played a role in spreading Mennonite Anabaptism which helped establish the Meserete Kristos Church. In 1951, Anna-Liisa and Sanfrid Mattson traveled from Finland to Ethiopia and established a Pentecostal mission in Addis Ababa, the country's capital. In 1960, a mission was created in Awasa by the Philadelphia Church Mission of the Swedish Pentecostal Movement. Pentecostalism, during the 1960s, attracted many students, and the movement grew enough that the Full Gospel Believers Church (FBGC) was created in 1967. Pentecostal practices eventually affected other Protestant denominations in Ethiopia, particularly the Lutheran church. Finnish and Swedish missionaries began the first Pentecostal initiatives in Ethiopia, largely independent of influence by American practices. In 1967, the Ethiopian Full Gospel Believers Church (Mulu Wengel) was founded. This church was the first independent Pentecostal church of Ethiopia and is still the largest Pentecostal group in Ethiopia. As churches were established, they relied on university students from Ethiopian Orthodox backgrounds to assume leadership roles within the Pentecostal churches. Methodism,Holiness movement, Presbyterianism, and other denominational orientations have had some underlying influence on Ethiopian-Eritrean Evangelicalism.

Protestant Christians still face persecution in rural regions and are assisted by the Voice of the Martyrs; however, there is a growing tolerance between the Ethiopian Orthodox, Muslims and the growing population of P'en'tay Christians in the urban areas of the country. With the dominance of the Ethiopian Orthodox Tewahedo and the growing Muslim population, the population of P'en'tay Christians was estimated around 16.15 million (19 percent of total population), according to the information released by the U.S. Department of State.

Catholicism (Catholic Church) 

The Ethiopian Catholic Church (; ) and the Eritrean Catholic Church (Tigrinya: ኤርትራዊት ቤተ ክርስቲያን; ) are metropolitan sui iuris Eastern particular church within the Catholic Church, established in 1930 in Ethiopia and established in 2015 by separation of its territory from that of the Ethiopian Catholic Church and the setting up in that territory of a new sui iuris metropolitan Eastern Catholic Church, respectively. Like the other Eastern Catholic Churches, the Ethiopian Catholic Church is in full communion with the Holy See. It holds the Christological doctrine of the Council of Chalcedon and accepts the universal jurisdiction of the pope. These points distinguish it from the Ethiopian Orthodox Tewahedo Church and the Eritrean Orthodox Tewahedo Church, an Oriental Orthodox Church which comprises most Christians in the the Ethiopian and Eritrean Community. The Ethiopian and Eritrean Catholic Churches follow the Alexandrian Rite used by the Ethiopian Orthodox Tewahedo Church, Eritrean Orthodox Tewahedo Church, the Coptic Orthodox Church of Alexandria, and the Coptic Catholic Church. As its liturgical language it employs Ge'ez, a Semitic language that fell out of daily use several centuries ago.

References

Ethiopia and Eritrea