Ishvara (IAST: Īśvara) is a concept in Hinduism, with a wide range of meanings in the various scools of Hinduism, also caused by the state of selfrealisation of their leaders.
In ancient indian texts, the word Īśvara can mean supreme soul, ruler, lord, king.
It appears rarely in Atharvaveda but in Samhitas of Yajurveda.
In medieval era texts, Ishvara means God, Supreme Being, personal god, or special Self, depending on the hinduist school.
* In Shaivism, Ishvara is synonymous with "Shiva", sometimes as Maheshvara or Parameshvara meaning the "Supreme lord" above the Trimurti, Ishana or Eeshana('invisible force which reigns the universe') of the 'pañcabrahmans', or also an Ishta-deva (personal god) for Sadhana.
* In kashmir Shaivism, Ishvara is just the ruler of the Ishvara-tattva, above him are Sadashiva, the primordial Shiva and Paramshiva.
* In Vaishnavism, Ishvara is synonymous with Vishnu. The Gita looks at Krishna as Parameshvara.
* In modern movements such as Arya Samaj and Brahmoism, Ishvara takes the form of a monotheistic God.
* In Ashtanga - Yoga school of Hinduism, Ishvara is the Lord which governs the lower worlds. Patanjali defines Isvara in verse 24 of book 1 as a special Self (puruṣa-viśeṣa).
* In the Advaita Vedanta school, Ishvara is a monistic universal Absolute that connects and is the Oneness in everyone and everything, a personification of the Nirguna-Brahman. Adi Shankara sees Him as the ruler of the Karma.
== Other Religions ==
In Mahayana Buddhism, the word Ishvara is used as part of the compound "Avalokiteśvara" ("lord who hears the cries of the world"), a female bodhisattva who has similarities with the hinduist devi Maheshvari. In Mahayana is Samantabhadra as personification of the good comparable with Ishvara.
As creator god Ishvara is comparable with the kabbalist Jah Jahwe Zebaoth and also with the islamic Allah.