Ogaden is a region in Ethiopia. It is a part of the Somali Region of the country. Historically Ogaden was sometimes known as Abyssian Somaliland. Ogadeni nationalists refer to it as Ogadenia and state that it is a separate nation under Ethiopian occupation. The Ogadeni people are predominantly ethnic Somali and Muslim.

The region, which is 369,000 square kilometres, borders Djibouti, Kenya, and Somalia, and has a population of seven million people. It was was colonized by Great Britain as a protectorate from the last quarter of the 19th century to the first half of the 20th century, before it was annexed by Ethiopia.

In the past, secessionist activities have involved the political goals and militaries of Ethiopia and Somalia. In the late 1970s, both countries fought the Ogaden War over control of this region and its peoples. At present, the main separatist group is the Ogaden National Liberation Front (ONLF) under its chairman Mohamed O. Osman .

Ogaden is at the center of the volatile Horn of Africa. Prominent Ogadeni include:

• Muslim military leader Ahmad ibn Ibrihim al-Ghazi, better known as Ahmed Gragn
• Somali poet and nationalist Sayid Mohamed Abdille Hassan