Ishvara (ईश्वर) is a concept in Hinduism, with a wide range of meanings that depend on the era and the school of Hinduism. In ancient texts of Hindu philosophy, depending on the context, Ishvara can mean supreme Self, ruler, lord, king, queen or husband. In medieval era Hindu texts, depending on the school of Hinduism, Ishvara means God, Supreme Being, personal God, or special Self.
Ishvara is primarily an epithet of Shiva. In Shaivism, Ishvara is an epithet of Shiva. For many Vaishnavas, it is synonymous with Vishnu, like in his epithet of Venkateswara. In traditional Bhakti movements, Ishvara is one or more deities of an individual's preference (Iṣṭa-devatā) from Hinduism's polytheistic canon of deities. In modern-day sectarian movements such as Arya Samaj and Brahmoism, Ishvara takes the form of a monotheistic God. In the Yoga school of Hinduism, it is any "personal deity" or "spiritual inspiration".
The root of the word Ishvara comes from īś- (ईश, Ish) meaning "capable of" and "owner, ruler, chief of". The second part of the word Ishvara is vara which means depending on context, "best, excellent, beautiful", "choice, wish, blessing, boon, gift", and "suitor, lover, one who solicits a girl in marriage". The composite word, Ishvara literally means "owner of best, beautiful", "ruler of choices, blessings, boons", or "chief of suitor, lover".
As a concept, Ishvara in ancient and medieval Sanskrit texts variously means God, Supreme Being, Supreme Self, Lord Shiva, a king or a ruler, a husband, the god of love, one of the Rudras and the number 'eleven'.
The word Īśvara does not appear in Rigveda. However, the verb īś- does appear in Rig veda, where the context suggests that the meaning of it is "capable of, able to". It is absent in Samaveda, is rare in Atharvaveda, but it appears in Samhitas of Yajurveda. The contextual meaning, however as the ancient Indian grammarian Pāṇini explains, is neither god nor supreme being.
The word Ishvara appears in numerous ancient Dharmasutras.