Unifying Hinduism: Philosophy and Identity in Indian Intellectual History is a 2010 book written by the American Indologist Andrew J. Nicholson, Associate Professor of Hinduism and Indian Intellectual History at the State University of New York (SUNY), on the history of Indian philosophy, describing the philosophical unification of Hinduism, which the author places in the Middle Ages. The book was published in the United States in 2010 in hardcover, with a paperback edition appearing in 2014. An Indian hardcover edition was published by Permanent Black in 2011. The book won the 2011 award for Best First Book in the History of Religions from the American Academy of Religion, and has been reviewed in numerous academic journals.

Unifying Hinduism contains 10 chapters. Much of the book focuses on the thought of the medieval Indian philosopher Vijñānabhikṣu. The book's central concern is to show that Vijñānabhikṣu provided a philosophical synthesis of diverse schools of Indian philosophy, thereby providing a philosophical unification of Hinduism long before the British colonial conquest and rule of India. This refutes claims that Hinduism only attained unity (or only was "invented") as a response to colonial influence.

After an introductory first chapter, the next five chapters focus on Vijñānabhikṣu's philosophical syntheses. Chapter 2, entitled "An Alternate History of Vedanta", sets the stage by tracing the history of Bhedābheda Vedānta, a comparatively neglected tradition that teaches the "difference and nondifference" of Brahman and the individual self. Vijñānabhikṣu's version of this "Difference and Non-Difference" Vedānta is described in Chapter 3.

Chapter 4 offers a historical overview of two important non-Vedānta, earlier orthodox Indian philosophies: the philosophical schools of Sāṃkhya and Yoga, focusing on their views of God, documenting that, contrary to the widespread view of Sāṃkhya as an entirely atheistic school of thought, most first millennium Sāṃkhya philosophers were theistic. Chapter 5, "Reading Against the Grain of the Sāṃkhyasūtras", focuses on a controversial assertion by Vijñānabhikṣu that some verses in the Sāṃkhyasūtras that explicitly argue against God's existence do not ultimately intend to deny God's existence, but represent merely a “temporary concession” (abhyupagamavāda) or “bold assertion” (prauḍhivāda). Finally, Chapter 6, "Yoga, Praxis, and Liberation", discusses Vijñānabhikṣu's commentary on Patañjali's Yogasūtras, arguing that Vijñānabhikṣu's commentaries on Vedānta, Sāṃkhya, and Yoga represent a unified whole.

Chapter 7, "Vedanta and Samkhya in the Orientalist Imagination", discusses how Vijñānabhikṣu was diversely viewed by 19th-century European scholars, who in some sense can be understood as "intellectual inheritors of Vijñānabhikṣu’s thought".

The next two chapters return to South Asian thought, with Chapter 8 focuses on Indian philosophical doxographies (categorizations) and Chapter 9, "Affirmers (Āstikas) and Deniers (Nāstikas) in Indian History", providing a history and preferred translation of the two terms āstika and nāstika, which are more often translated as "orthodox" and "heterodox". The concluding tenth chapter, "Hindu Unity and the Non-Hindu Other", discusses the timing of the unification of Hindu philosophical schools, suggesting that the stimulus was the presence of Islam in the Indian subcontinent.

Unifying Hinduism won the 2011 award for Best First Book in the History of Religions from the American Academy of Religion.

Reviews have appeared in academic journals such as the Journal of the American Academy of Religion, Religious Studies Review, Sophia, Journal of the American Oriental Society, Journal of Asian Studies, Journal of Hindu Studies, South Asian History and Culture, Literature and Theology, Choice, and Metapsychology. Unifying Hinduism has also been discussed in the 2014 book Indra's Net: Defending Hinduism's Philosophical Unity, written by Indian-American author Rajiv Malhotra.