The Luo are part of the River-Lake Nilotics and are related to the Nuer and the Dinka in the Sudan. Their original homeland is said to have been at Rumbek in southern Sudan. During the 15th century, they were faced with many calamities which forced them to move away in search of new areas for settlement. Some reasons given for Luo migration include: overpopulation, human and animal diseases, natural hazards like droughts and floods, external pressure from the Galla tribesmen, as well as internal conflicts. Some moved northwards to Shilluk, others moved eastwards to Anuak and some of them continued through Ethiopia, past Agoro Hills to northern Uganda. The major group, however, is said to have moved from Rumbek southwards along the Nile, and settled at Pubungu near Pakwach. This group is said to have been under the leadership of Olum.
Olum had three sons namely: Gapiir (Nyapir), Labongo (Kyebambi) and Tiful. It is said that at Pubungu, Gapiir and Labongo conflicted over the royal spear which was their symbol of power. Thereafter they separated. Gapiir leading a group of people, crossed the Nile and went to the land of the Lendu and Okebu in present West Nile. His people intermarried with the Lendu and Okebu and produced the Alur. The Alur speak Luo and maintain other elements of Luo culture. Tiful is said to have moved to West Nile also but little is known about his movements and settlements there.
Labongo moved north-eastwards from Pubungu towards present Acholi. In the process, Labongo’s group intermarried with and assimilated some Sudanic-speaking peoples in northern Uganda and produced the Acholi. By the beginning of the 18th Century, they were firmly settled in Acholi. There, they encountered the Langi who had been living in Acholi for about two hundred years. Soon conflicts developed between the Acholi and the Langi and this forced the Langi to move southwards to the Lake Kioga region. The Acholi continued to interact and intermarry with the Langi. In the process, the Langi lost their Ateker language and began to speak Luo. They also lost their pastoral element and became settled agriculturists because the area around L. Kioga was not conducive to pastoralism. Therefore although the Langi speak Luo, in actual fact, they are not Luo but Nilo-Hamites.
Another group of Luo moved southwards from Pubungu and settled in Pawir which today is settled by the Bagungu. A small group known as the Biito-Luo led by Isingoma Mpuga Rukidi moved on and settled in Bunyoro peacefully and established the Babiito dynasty. Their political influence was limited to a new kingdom which came to be known as Bunyoro-Kitara. It lasted until 1967 when the new constitution introduced by Milton Obote abolished kingdoms in Uganda and set up a republic. Those Luo who went to Bunyoro were assimilated. They lost their language and culture and became Bantuised. However, they introduced pet names among the Banyoro. It is not clear whether there was any interaction between the Bachwezi and Babiito although traditions attempt to link them.
Between the middle of the l6th century and the beginning of the 17th century, some Luo groups pushed eastwards. One group led by Adhola, settled in Budama around the first half of the 17th century. They chose to settle in thickly forested area as a defence against the attacks from Bantu neighbours who had already settled there. This self-imposed isolation helped them to maintain their language and culture amidst Bantu and Ateker communities. Between 1550 and 1800, other Luo groups crossed into the Nyanza province of Kenya. By 1800, the Luo had completed their migrations and settlement in present northwestern, northern and eastern Uganda.