Omniscience is the property of possessing maximal knowledge. In Hinduism, Buddhism, Sikhism and the Abrahamic religions, it is often attributed to a divine being or an all-knowing spirit, entity or person. In Jainism, omniscience is an attribute that any individual can eventually attain. In Buddhism, there are differing beliefs about omniscience among different schools.

The word omniscience derives from the Latin word sciens ("to know" or "conscious") and the prefix omni ("all" or "every"), but also means "all-seeing".

The topic of omniscience has been much debated in various Indian traditions, but no more so than by the Buddhists. After Dharmakirti's excursions into the subject of what constitutes a valid cognition, Śāntarakṣita and his student Kamalaśīla thoroughly investigated the subject in the Tattvasamgraha and its commentary the Panjika. The arguments in the text can be broadly grouped into four sections:

Some modern Christian theologians argue that God's omniscience is inherent rather than total, and that God chooses to limit his omniscience in order to preserve the free will and dignity of his creatures. John Calvin, among other theologians of the 16th century, comfortable with the definition of God as being omniscient in the total sense, in order for worthy beings' abilities to choose freely, embraced the doctrine of predestination.

In the Bhakti tradition of Vaishnavism, where Vishnu is worshipped as the supreme God, Vishnu is attributed with numerous qualities such as omniscience, energy, strength, lordship, vigour, and splendour.

God in Islam is attributed with absolute omniscience. God knows the past, the present, and the future. It is compulsory for a Muslim to believe that God is indeed omniscient as stated in one of the six articles of faith which is:

Say: Do you instruct God about your religion? But God knows all that is in the heavens and on the earth; God is Knowing of all things

— Quran 49:16