Sundar obtained a Bachelor of Arts degree in Philosophy, Politics and Economics from Somerville College, Oxford in 1989 and Master of Arts, Master of Philosophy and Ph.D. in Anthropology from Columbia University in 1989, 1991 and 1995, respectively.^[2] She has previously worked at Jawaharlal Nehru University, The Institute of Economic Growth and Edinburgh University. Sundar was editor of Contributions to Indian Sociology from 2007 to 2011 and serves on the boards of several journals. ^{[citation needed]}

In 2007, Sundar along with others filed public interest litigation against human rights violations in Chhattisgarh, arising out of the Salwa Judum vigilante movement. In 2011, the Supreme Court of India banned Salwa Judum, ordered compensation for all those affected, and investigation and prosecution of those responsible. It also ordered the disbanding and disarming of Special Police Officers, many of whom were underage youth who had been armed by the state to fight Naxalites.^[4]

In October 2016, the Central Bureau of Investigation on the Supreme Court's orders in the ongoing case filed by Sundar and others, filed chargesheets against seven Special Police Officers and 26 Salwa Judum leaders for their role in the burning of three villages in the Sukma district in March 2011 and the attack on Swami Agnivesh. The arson had allegedly been accompanied by rapes and murders of villagers.^[5]

Almost immediately afterwards, the police burnt effigies of Sundar and other activists, and the Bastar police filed a first information report against her on 4 November 2016, as an alleged co-conspirator in the murder of Shamnath Baghel, a tribal in the Sukma district of Chattisgargh.^[6] The wife of the victim told a national television channel, NDTV, that she had not named anyone, after police cited her complaint to allege Sundar and another professor were suspects.^[7][8]

The National Human Rights Commission summoned the IGP of Bastar Range SRP Kalluri and Chhattisgarh Chief Secretary for retaliation, and has said there was no apparent connection between the visit of Sundar and other human rights activists and the murder of Shamnath Baghel.^[9] The Indian Supreme Court recorded the Chhattisgarh government's statement that they would not arrest or investigate Sundar, and ruled that if the Chhattisgarh state government wanted to undertake any investigation, they should give four weeks' notice during which time Sundar and others could approach the Court. Eventually, her name was dropped by the Chhattisgarh police from the murder case in February 2019, after the change of government in Chhattisgarh,^[10] citing 'lack of direct evidence'.^[11]

Sundar has long been outspoken about the issue of academic freedom. In 2019, she told Times Higher Education that the blackout in Kashmir had been a "devastating blow," that the situation has worsened nationwide since Modi's election in 2014, and that the lack of liberties could harm India's attempts at climbing university rankings. ^[12]

In summer 2020, she submitted a paper on academic freedom to the United Nations.^[13]

Selected publications of Sundar include:

• The Burning Forest: India's War in Bastar (Juggernaut Press, 2016),
• The Scheduled Tribes and their India (edited volume, OUP, 2016),
• Civil Wars in South Asia: State, Sovereignty, Development (Sage 2014, co-edited),
• Subalterns and Sovereigns: An Anthropological History of Bastar (2nd ed 2007, 1997),
• Branching Out: Joint Forest Management in India (co-authored, OUP, 2001),
• Legal Grounds: Natural Resources, Identity and the Law in Jharkhand (edited OUP, 2009),
• Anthropology in the East: The founders of Indian sociology and anthropology (co-edited, Permanent Black, 2007)
• A New Moral Economy for India's Forests (co-edited, Sage, 1999)

Sundar is married to Siddharth Varadarajan, former chief editor of The Hindu—an Indian English-language national newspaper—and a founding editor of The Wire.^[14] Her parents, S Sundar and Pushpa Sundar were both Indian Administrative Service officers of the Gujarat cadre belonging to the 1963 batch. She has an elder sister, Aparna, who is also a social activist.^{[citation needed]}