Arusha Region (Swahili: Mkoa wa Arusha) is one of Tanzania's 31 administrative regions and is located in the northeast of the country. The region's capital and largest city is the city of Arusha. The region is bordered by Kajiado County and Narok County in Kenya to the north, the Kilimanjaro Region to the east, the Manyara and Singida Regions to the south, and the Mara and Simiyu regions to the west. Arusha Region is home to Ngorongoro Conservation Area, a UNESCO World Heritage Site. The region is comparable in size to the combined land and water areas of the state of Maryland in the United States.

Arusha Region is a tourist destination in Africa and is the hub of the northern Tanzania safari circuit. The national parks and nature reserves in this region include Ngorongoro Conservation Area, Arusha National Park, the Loliondo Game Controlled Area, and part of Lake Manyara National Park. Remains of 600-year-old stone structures are found at Engaruka, just off the dirt road between Mto wa Mbu and Lake Natron. With a HDI of 0.721, Arusha is among the most developed regions of Tanzania being Tanzania's top 3 most resourceful region.

The "Arusha" Region is named after the Arusha people, a Bantu ethnic group that originally migrated from Arusha Chini in Kilimanjaro Region around 400 years ago.

Arusha Region is home to Laetoli and Olduvai Gorge national archaeological sites both locations with discoveries of prehistoric hominids.

The first communities in southwestern Arusha Region's Arusha District, Arusha Rural District and Meru District, were the now extinct Koningo people, an ancient hunter-gatherer group that lived around the slopes of Mount Meru for centuries.

The second community to settle in the region is the Meru People, whom immigrated there from the Usambara Mountains in Tanga Region. They settled on the southeastern slopes of the mountain and started to farm the land. The third wave of settlers were the Arusha people a subgroup of the Pare people migrated from Arusha Chini in Kilimanjaro Region. Some Parakuyo Masai in the west, who were the last group to immigrate to Arusha Region in the 1830s, assimilated into the Arusha community and influenced the Arusha into adopting the Masai language.

In the 1880s a pandemic of rinderpest killed thousands of cattle and forced a large section of the Masai people in the west and integrated into Arusha agriculturally based society. In southeastern portion of the region in Karatu District and southern Ngorongoro District is the ancestral home to the Hadzabe People, who are the only surviving hunter gather communities left in the country.

Moreover, most of the Ngorongoro District, Monduli District and Longido District of the present area of Arusha Region are home to the Maasai, who immigrated from South Sudan, started moving southward around the 16th century CE toward Kenya, and finally reached the northwestern Arusha Region in the 1830s. The Masai were the last precolonial community to settle in the present-day Arusha Region.