Tahtay Adiyabo (Tigrinya "Lower Adiyabo") is one of the woredas in the Tigray Region of Ethiopia. Part of the Semien Mi'irabawi Zone, Tahtay Adiyabo is bordered on the south by the Asigede Tsimbela, on the southwest by the Tekezé River which separates Tahtay Adiyabo from the Mi'irabawi Zone, on the north by Eritrea, and on the east by La'ilay Adiyabo; part of the northern border with Eritrea is delineated by the Mareb River. The northernmost point of this woreda is the northernmost point of Ethiopia. Towns in this woreda include Addi Awuala, Addi Hageray, and Badme. Town of Shiraro is surrounded by Tahtay Adiyabo.
On 26 September 1976, on the eve of Meskel, the Tigrayan People's Liberation Front (TPLF) turned back an advance by an armed detachment of 250 Ethiopian Democratic Union fighters at Chiameskebet, a village near Shiraro, on 26 September 1976, forcing them to retreat across the Tekezé. Both sides suffered heavy casualties; amongst the TPLF wounded was their general, Mehari Tekle ("Mussie"), who was fatally wounded in the battle and died a few days later.
Flooding by the Tekezé in August 2006 damaged 68.5 hectares planted in fruits and vegetables and buried 21 water pumps. A violent storm in the second week of the same month also damaged 48.5 hectares of crops.
Based on the 2007 national census conducted by the Central Statistical Agency of Ethiopia (CSA), this woreda has a total population of 90,144, an increase of 80,934 over the 1994 census, of whom 45,834 are men and 44,310 women; 6,377 or 7.07% are urban inhabitants. With an area of 3,841.51 square kilometers, Tahtay Adiyabo has a population density of 23.47 people per square kilometer, which is less than the Zone average of 40.21. A total of 20,553 households were counted in this woreda, resulting in an average of 4.39 persons to a household, and 19,141 housing units. The majority of the inhabitants said they practiced Ethiopian Orthodox Christianity, with 95.59% reporting that as their religion, while 3.15% of the population were Muslim.