The Luo of Kenya and Tanzania are a Nilotic ethnic group native to western Kenya and the Mara Region of northern Tanzania in East Africa. The Luo are the fourth-largest ethnic group (10.65%) in Kenya, after the Kikuyu (17.13%), the Luhya (14.35%) and the Kalenjin (13.37%). The Tanzanian Luo population was estimated at 1.1 million in 2001 and 3.4 million in 2020. They are part of a larger group of related Luo peoples who inhabit an area ranging from South Sudan, southwestern Ethiopia, northern and eastern Uganda, Chad, Central African Republic, Nigeria, northeastern Congo-Kinshasa, southwestern Kenya and northern Tanzania.

They speak the Luo language, also known as Dholuo , which belongs to the Western Nilotic branch of the Nilotic language family. Dholuo shares considerable lexical similarity with languages spoken by other Luo peoples.

The Luo are descended from migrants who moved into western Kenya from Uganda between the 15th and 20th centuries in four waves. These migrants were closely related to Luo peoples found in Uganda, especially the Acholi and Padhola people. As they moved into Kenya and Tanzania, they underwent significant genetic and cultural admixture as they encountered other communities that were long established in the region.