In Jainism, "aathai" (also spelled as "athai" or "aathai parva") refers to an eight-day period of special spiritual observance, most commonly associated with Paryushana, one of the most important Jain festivals. During the aathai, Jains engage in intensified practices such as fasting (upvaas), prayer, meditation, self-reflection, and listening to discourses on Jain scriptures.

The word "aathai" itself means "eight" in Gujarati and some other Indian languages. In the context of Paryushana, Shwetambar Jains observe the festival for eight days (hence, "aathai"), while Digambar Jains observe it for ten days (called Das Lakshan Parva).

Aathai is considered a time for spiritual renewal, seeking forgiveness, and purification of the soul through right conduct and repentance.