Hausa-Fulani is a term used to refer collectively to the Hausa

Hausa people

The Hausa are one of the largest ethnic groups in West Africa. They are a Sahelian people chiefly located in northern Nigeria and southeastern Niger, but having significant numbers living in regions of Cameroon, Ghana, Cote d'Ivoire, Chad and Sudan...

 and Fulani

Fula people

Fula people or Fulani or Fulbe are an ethnic group spread over many countries, predominantly in West Africa, but found also in Central Africa and Sudanese North Africa...

 people of West Africa

West Africa

West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

. The two are grouped together because since the Fulani War

Fulani War

The Fulani War of 1804-1810, also known as the Fulani Jihad or Jihad of Usman dan Fodio, was a military conquest in present day Nigeria and Cameroon. Expelled from Gobir by his former student Yunfa in 1802, Islamic reformer Usman dan Fodio assembled a Fulani army to lead in jihad against the Hausa...

 their histories have been largely intertwined. For example, when the Fulani took over Hausa city-state of Kano

Kano

Kano is a city in Nigeria and the capital of Kano State in Northern Nigeria. Its metropolitan population is the second largest in Nigeria after Lagos. The Kano Urban area covers 137 sq.km and comprises six Local Government Area - Kano Municipal, Fagge, Dala, Gwale, Tarauni and Nassarawa - with a...

 during the Fulani War, the new emirs ended up speaking the Hausa language

Hausa language

Hausa is the Chadic language with the largest number of speakers, spoken as a first language by about 25 million people, and as a second language by about 18 million more, an approximate total of 43 million people...

 instead of Fulfulde

Fula language

The Fula or Fulani language is a language of West Africa. It is spoken as a first language by the and related groups from Senegambia and Guinea to Cameroon and Sudan...

.

The Hausa-Fulani are one out of Nigeria's three major ethnic groups. The Hausa-Fulani account for 28-30% of Nigeria's population.