The Womb Realm, based on the Mahāvairocana Tantra, is the metaphysical space inhabited by the Five Wisdom Buddhas. Its name comes from chapter 2 of the sutra, which states that the buddha Mahāvairocana (Dainichi Nyorai) revealed the mandala's secret teachings to his disciple Vajrasattva (Kongousatta) from his "womb of compassion".

The Womb Realm mandala, along with the Diamond Realm mandala, form the core of Tendai and Shingon Buddhist rituals and are usually hung on the east and west walls of Shingon temple halls.

In depictions of the Womb Realm, Mahāvairocana sits at the center of an eight-petaled lotus wearing a jewelled crown. Four Buddhas representing the four directions, Ratnaketu (Houtou Nyorai), Saṃkusumitarāja (Kaifukeou Nyorai), Amitābha (Amida Nyorai), and Divyadundubhimeghanirghoṣa (Tenkuraion Nyorai), are placed orthogonal to Mahāvairocana. Four bodhisattvas, Samantabhadra (Bugen Bosatu), Manjushri (Monju Bosatsu), Guanyin (Kannon), and Maitreya (Miroku Bosatsu), are illustrated between the Buddhas.

Hundreds more divinities reside in eleven more halls branching from the center.