In Indian religions and society, an acharya (IAST: ācārya; Sanskrit: आचार्य; Tamil: அசாரி āsāri; Pali: acariya) is a Brahmin head guide or instructor in religious matters; founder, or leader of a sect; or one who sits on Gadi (seat); or a highly learned man or a title affixed to the names of learned men. The designation has different meanings in Hinduism, Buddhism, Jainism and secular contexts. The surname is also very common in the Indian state of West Bengal.
Acharya is also used to address a teacher or a scholar in any discipline, e.g.: Bhaskaracharya, the mathematician. It is also a common suffix in Brahmin names, e.g.: Krishnamacharya, Bhattacharya. In South India, this suffix is sometimes shortened to Achar, e.g.: TKV Desikachar. In the social order of some parts of India, acharyas are considered as the highest amongst the Viswakarma Brahmin community.
The term "Acharya" is most often said to include the root "char" or "charya" (conduct). Thus it literally connotes "one who teaches by conduct (example)," i.e. an exemplar.
In Hinduism, an acharya (आचार्य) is a formal title of a teacher or guru, who have owned the degree in the Vedanga. In rare cases, the title may denote someone considered to be a mahāpuruśa (महापुरुश, divine personality) who is believed to have descended as an avatāra (अवतार, incarnation) to teach and establish bhakti in the world and write on the siddhānta (सिद्धांत, doctrine) of devotion to Bhagwan (भगवान्, lord, God, blessed one, see also iśvara).
The Five Main Acharyas in the Hindu tradition are:
- Adi Sankaracharya
- Nimbarkacharya
- Vallabhacharya
In Jainism, an dev:koti is a monk who is one of the Pañca-Parameṣṭhi and thus worthy of worship. An acharya is the highest leader of a Jain order. He is the final authority in his monastic order and has the authority to ordain new monks and nuns. He is also authorized to consecrate new idols, although this authority is sometimes delegated to scholars designated by him.
Some famous Jain acharyas in approximate chronological order, are:
- Sudharma Swami
- Bhadrabahu Acharya (undivided Jain community, Chandragupta Acharya was his disciple) (325 BCE)
- Sthulabhadra (Svetambara)
- Kundakunda (Digambara, 2nd century CE)
- Jaysen Acharya (Digambara) - wrote tika on Samaysaar - i.e. commentary on Samaysaar Shastra
- Amrutchandra Acharya (Digambara) - wrote a commentary called Atmakhyati on the Samaysaar Shastra.
- Samantabhadra (Digambara, 3rd–4th century CE)
- Siddhasena Divakara (claimed by both, 5th century CE)
- Haribhadra (Svetambara), 700–750 CE)
- Virasena (Digambara), 790–825 CE)
- Jinasena (Digambara), preceptor of the Rashtrakuta Dynasty, (800–880 CE).
- Nemichandra (Digambara)
- Acharya Hemachandra (Svetambara), preceptor of Kumarapala, (1089–1172 CE)
- Jagadguru Hiravijaya (Svetambara), who was invited by Akbar, the Mughal emperor
- Acharya Rajendrasuri (Svetambara, 1827–1906)
- Shantisagar (Digambara, 1872–1955)
- Aryanandi (Digambara, 20th Century)
Modern Jain acharyas include Digambara Acharya Vidyasagar and Vidyanand and Svetambara Padma Sagar Suri, Subodhsagar Suri, Yashodev Suri, and Jayantsain Suri. In the Svetambar Terapanthi subsect are Acharya Bhikshu, Acharya Tulsi and Acharya Mahapragya and in the Sthanakvasi subsect Sushil Kumar Acharya have been the leading acharyas.
- Srila Bhaktivinoda Thakura
- Srila Bhaktisiddhanta Sarasvati Thakura
- Srila A.C Bhaktivedanta Swami Prabhupada, Founder-Acharya of ISKCON
In scientific/mathematical scholarship
In Sanskrit institutions Acharya is a Post Graduate Degree.
- Platts, John T. (1884). A dictionary of Urdu, classical Hindi, and English. London: W. H. Allen & Co.
- Glossary - Encyclopedia of Authentic Hinduism
- [viswakarma community] Although famous for being the proponent of advaita vad, he established the supremecy of bhakti to Krishn.
- He propagated the bhakti of Bhagwan Vishnu. Source: Ramanujacharya
- His philosophy is called dvaita vad. His primary teaching is that "the only goal of a soul is to selflessly and wholeheartedly love and surrender to God" Source: 
- His writings say that Radha Krishn are the supreme form of God.