Ahaścara is one of the names of God Śiva , described in Śivasahasranāmastotra (Sivasahasranamastotra; The Hymn of the Thousand Names of Siva). There Śiva (Siva) is called both Ahaścara (Ahaschara) and Naktañcara (Naktanchara). In course of explaining the name, Nīlakaṇṭha (Nilakantha), the commentator, has said —
ahaścara devādiḥ naktañcaro rākṣasādistadu bhayarūpaḥ.

Here Aha means day, and Nakta means night. According to mythological conception, gods, human beings and ordinary creatures move in daytime, do their usual works, and sleep at night. On the other hand, the Asura(s) usually move and function at night. Thus, by these two names, Ahaścara and Naktañcara — God Śiva is conceptualised as the manifestation of all kinds of creatures, gods, demons,human beings, monsters –all orders of living beings emerged from Śiva, who is the Creator of the world. He resides in every being in the form of Jīvātmā (Jivatma). So he is called both Ahaścara and Naktañcara.