Pannychis (, ), from Greek words ('all, every') and ('night'), may refer to:
- An all-night feast or ceremony of the ancient Eleusinian Mysteries
- Pannychis, a courtesan given by the Jewish king Herod the Great to the king of Cappodocia as thanks for reconciling a Herod family dispute<!-- -->
- Vigil, a period of purposeful sleeplessness, an occasion for devotional watching, or an observance
- Panichida (панихида), the name for Memorial service (Orthodox) in Slavic languages
- Pannychis (beetle), a longhorn beetle genus in the tribe Saperdini