Dadi is a community development block (CD block) that forms an administrative division in the Hazaribagh Sadar subdivision of the Hazaribagh district in the Indian state of Jharkhand.

Hazaribagh district is spread over a part of the Chota Nagpur Plateau. The central plateau, averaging a height of 2,000 ft (610 m), occupies the central part of the district. On all sides, except on the western side, it is surrounded by the lower plateau, averaging a height of 1,300 ft (396 m), the surface being undulating. In the north and the north-west the lower plateau forms a fairly level tableland till the ghats, when the height drops to about 700 ft (213 m) and slopes down gradually. The Damodar and the Barakar form the two main watersheds in the district. DVC has constructed the Konar Dam across the Konar River. It is a forested district with cultivation as the main occupation of the people. Coal is the main mineral found in this district. China clay is also found in this district. Inaugurating the Pradhan Mantri Ujjwala Yojana in 2016, Raghubar Das, Chief Minister of Jharkhand, had indicated that there were 23 lakh BPL families in Jharkhand. There was a plan to bring the BPL proportion in the total population down to 35%.

Right from its inception in 2000. Jharkhand was a “laboratory” for Naxalites to experiment with their ideas of establishing a parallel government. As of 2005, 16 of the 22 districts in the state, including Hazaribagh district, was transformed into a “guerrilla zone”. The movement was not restricted to armed operations but included kangaroo courts called "jan adalats", elected village bodies and people's police. Jharkhand, with a dense forest cover over a large part of the state, offers a favourable terrain for the Naxalites to build their bases and operate. Annual fatalities in Jharkhand were 117 in 2003 and 150 in 2004. In 2013 Jharkhand was considered one of the two states in the country most affected by Left wing extremism and Jharkhand police set up an exclusive cell to deal with Maoist activities. However, in the same year, when Jharkhand police identified 13 focus areas for combating Maoist extremism, Hazaribagh district was not one of them.

Dari, a census town in Dadi CD Block, is located at 23°42′48″N 85°22′52″E / 23.71333°N 85.38111°E / 23.71333; 85.38111.

Dadi CD block is bounded by Churchu CD block on the north, Mandu CD block, in Ramgarh district, on the east, Ramgarh and Patratu CD blocks, in Ramgarh district, on the south and Barkagaon CD block on the west.

Dadi CD block has an area of 145.43 km². As of 2011, Dadi CD block had 14 gram panchayats, 24 inhabited villages and 3 census towns (Dari, Religara alias Pachhiara, Gidi).Gidi police station serves this CD block, Headquarters of this CD block is at Dari.

According to the 2011 Census of India, Dadi CD block had a total population of 77,770, of which 49,770 were rural and 2,800 were urban. There were 40,012 (51%) males and 37,758 (49%) females. Population in the age range 0–6 years was 10,913. Scheduled Castes numbered 10,134 (13.03%) and Scheduled Tribes numbered 20,959 (26.95%).

Census towns in Dadi CD block are (2011 census figures in brackets): Dari (6,405), Religara alias Pachiari (8,239) and Gidi (13,356).