Mahāvākya

प्रज्ञानम् ब्रह्म

prajñānam brahma

Pure consciousness (prajñānam) is the Absolute Reality (brahma). — "Aitareya Upanishad" 3.3 of the "Rigveda"

अहं ब्रह्मास्मि

ahaṃ brahmāsmi

I (ahaṃ) am (asmi) the Absolute Reality (brahma). — "Brihadaranyaka Upanishad" 1.4.10 of the "Yajurveda"

तत् त्वम् असि / तत्त्वमसि

tat tvam asi

That (tat) you (tvam) are (asi). — "Chandogya Upanishad" 6.8.7 of the "Samaveda"

अयम् आत्मा ब्रह्म

ayam ātmā brahma

This (ayam) soul (ātmā) is the Absolute Reality (brahma). — "Mandukya Upanishad" 1.2 of the "Atharvaveda"