Upanishads classified.

Upanishad coming under Rig VEDA.
Aitareya
Aksha malika
Atma bodha
Bahuricha
Kaushitaki brahamana
Mudgala
Nada bindu
Nirvana
Saubhagyalakshmi
Tripura
Upanishad from Krishna Yajurveda
Akshi
Amrita bindu
Amrita Nada
Avadhuta
Brahma
Brahma vidya
Dakshinamurti
Dhayana bindu
Ekakshara
Garbha
Kaivalya
Kalagni rudra
Kali santarana
Katha
Katharudra
Kshurika
Maha Narayana Yajniki
Psncha brahma
Pransgnihotra
Rudra hridaya
Sarasvati rahasya
Sariraka
Sarva sara
Skanda
Suka rahasya
Svetasvatara
Taittiroya
Tejo bindu
Varaha
Yoga kunfalini
Yoga sikha
Yoga tattva
Upanishad from Shukla Ysjur VEDA
Adhyatma
Advaya taraka
Bhikshuka
Brihadsrsnyaka
Hamsa
Isavasya
Jabala
Mandalabrahma
Mantrika
Muktika
Niralamba
Paingala
Paramahamsa
Satyayaniya
Subala
Tara Sara
Trisikhi Brahmana
Turiystita avadhuta
Yajnavalkya
Upanishad from Samveda
Aruni aruneyi
Avyakla
Chandogya
Darsana
Jabali
Kena
Kundika
Maha
Maitrayani
Maitreya
Rudraksha jabala
Sannyasa
Savitri
Vajrasuchika
Vasudeva
Yuga chudamani
Upanishad from Atharva-Veda
Annapurna
Atharvasikha
Atharvasiras
Atma
Bhasma jabala
Bhavana
Briahad jabala
Dattatreya
Devi
Ganapati
Garuda
Gopala tapaniya
Hayagriva
Krishna
Maha vakya
Mandukya
Mundaka
Narada parivrajaka
Nrisimha tapaniya
Para brahma
Paramahamsa parivrajaka
Pasupata Brahmana
Prasna
Rama rahasya
Rama tapaniya
Sandilya
Sarabra
Sita
Surya
Tripadubhuti maha Narayana
Tripura tapini