Upanishad (Sk.) Translated as “esoteric doctrine,” or interpretation of the Vedas by the Vedanta methods. The third division of the Vedas appended to the Brahmanas and regarded as a portion of Sruti or “revealed” word. They are, however, as records, far older than the Brahmanas—with the exception of the two, still extant, attached to the Rig-Veda of the Aitareyins [i.e. Aitareya and Kashitaki Upanishads]. The term Upanishad is explained by the Hindu pundits as “that which destroys ignorance, and thus produces liberation” of the spirit, through the knowledge of the supreme though hidden truth . . . It is from these treatises of the Upanishads—themselves the echo of the primeval Wisdom-Religion—that the Vedanta system of philosophy has been developed. . . . The accepted number of these treatises is 150, though now no more than about twenty are left unadulterated. They treat of very abstruse, metaphysical questions, such as the origin of the Universe; the nature and the essence of the Unmanifested Deity and the manifested gods the connection, primal and ultimate, of spirit and matter; the universality of mind and the nature of the human Soul and Ego. 

The Upanishads must be far more ancient than the days of Buddhism, as they show no preference for, nor do they uphold, the superiority of the Brahmans as a caste. On the contrary, it is the (now) second caste, the Kshatriya, or warrior class, who are exalted in the oldest of them. As stated by Professor Cowell in Elphinstone’s History of India—“they breathe a freedom of spirit unknown to any earlier work except the Rig Veda. . . The great teachers of the higher knowledge and Brahmans are continually represented as going to Kshatriya Kings to become their pupils.” The “Kshatriya Kings” were in the olden times, like the King Hierophants of Egypt, the receptacles of the highest divine knowledge and wisdom, the Elect and the incarnations of the primordial divine Instructors—the Dhyâni Buddhas or Kumâras. . . .—H. P. Blavatsky, Theosophical Glossary


Although there are hundreds of texts which may use the term “Upanishad,” the most commonly recognized Upanishads are the 108 of the Muktika Canon. The Muktika Upanishad lists these 108, but also sets apart 10 of the most critical and primary of Upanishads, known as the Mukhya (“Principal”) or simply the Dasha (“Ten”) Upanishads. These 10, along with 3 others (Kaushitaki, Maitrayaniya, and Shvetashvatara), are associated with or directly embedded into the body of Vedic literature (the Vedas and their glosses, the Brahmanas and Aranyakas). This Vedic literature is generally divided into two major categories, the karma-kanda (the section of works) and the jnana-kanda (section of wisdom). These oldest and most important Upanishads represent the basis of the Wisdom-Section.

The Muktika Upanishad suggests to begin one’s study with the Mandukya Upanishad, then proceed to study the 10 Mukhya Upanishads (Sankaracharya recommends to do this in the order given in the Muktika, i.e. Isa to Brihadaranyaka), then expand one’s study to include the first 32 Upanishads, then finally the full 108. The Mandukya Upanishad provides a basic framework on which the Vedanta understanding of Macro- and Microcosm rest. The remaining Mukhya Upanishads expand upon it and examine both its doctrinal details and provide an overview of the Path to realization and liberation. The rest of the Upanishads compliment these with details into specific categories of ideas and practices. The full scope of the Upanishads form the stable basis upon which rests the whole of the later Vedanta philosophy.


The 108 Upanishads
Arranged by Veda and School, with Numbering from the Muktika Upanishad 

(Note: sources and scholars vary in how the following are arranged. We have used the numbering and Veda groupings from the Muktika Upanishad, and the classifications into Schools as used in Adyar’s 108 Upanishads series.)

Veda Mukhya Sāmānya Sannyāsa Śākta Vaiṣṇava Śaiva Yoga
Ṛigveda 8. Aitareya 25. Kauśītāki,
42. Ātmabodha,
57. Mudgala
47. Nirvāṇa 82. Tripura,
105. Saubhāgya­lakṣmī,
107. Bahvṛca

67. Akṣamālika 38. Nādabindu
Samaveda 2. Kena,
9. Chāndogya
24. Maitrāyaṇi,
36. Vajrasūchi,
61. Mahat,
75. Sāvitrī
16. Āruṇi,
29. Maitreya,
65. Sannyāsa,
74. Kuṇḍika

56. Vāsudeva,
68. Avyakta
88. Rudrākṣajābāla,
104. Jābāli
46. Yogachūḍāmaṇi,
90. Darśana
Krishna Yajurveda 3. Kaṭha,
7. Taittirīya
17. Garbha,
33. Sarvasāra,
35. Śukarahasya,
51. Skanda,
62. Śārīraka,
69. Ekākṣara,
72. Akṣi,
94. Prāṇāgnihotra
11. Brahma,
79. Avadhūta,
83. Kaṭharudra
106. Sarasvatīra­hasya 18. Nārāyaṇa,
52. Mahānārāyaṇa**
103. Kalisaṇṭāraṇa
12. Kaivalya,
14. Śvetāśvatara,
28. Kālāgnirudra,
49. Dakṣiṇāmūrti,
85. Rudrahṛdaya,
93. Pañcabrahma
20. Amṛtabindu,
21. Amṛtanāda,
31. Kṣurika,
37. Tejobindu,
39. Dhyānabindu,
40. Brahmavidyā,
41. Yogatattva,
63. Yogaśikhā,
86. Yogakuṇḍalini,
98. Varāha
Shukla Yajurveda 1. Īśāvāsya,
10. Bṛhadāraṇyaka
30. Subāla,
32. Mantrikā,
34. Nirālamba,
59. Paiṅgala,
73. Adhyātmā,
108. Muktikā
13. Jābāla,
19. Paramahaṃsa,
60. Bhikṣuka,
64. Turīyātīta,
97. Yājñavalkya,
99. Śāṭyāyani

91. Tārasāra

15. Haṃsa,
44. Triśikhi-brāhmaṇa,
48. Maṇḍala­brāhmaṇa,
53. Advayatāraka,
Atharvaveda 4. Praśna,
5. Muṇḍaka,
6. Māṇḍūkya

70. Annapūrṇa,
71. Sūrya,
76. Ātmā
43. Nārada­parivrājaka,
66. Paramahaṃsa­­parivrājaka,
78. Parabrahma
45. Sītā,
80. Tripurātapani,
81. Devī,
84. Bhāvana
27. Nṛsiṃhatāpanī (purva),*
27. Nṛsiṃhatāpanī (uttara),*
52. Tripādvibhuti-Mahānārāyaṇa**,
54. Rāmarahasya,
55. Rāmatāpaṇi,
95. Gopālatāpani,
96. Kṛṣṇa,
100. Hayagrīva,
101. Dattātreya,
102. Gāruḍa
22. Atharvaśira,
23. Atharvaśikha,
26. Bṛhajjābāla,
50. Śarabha,
87. Bhasmajābāla,
89. Gaṇapati
58. Śāṇḍilya,
77. Pāśupata,
92. Mahāvākya
The 108 Upanishads
with Traditional Numbering from the Muktika Upanishad

1. Īśāvāsya
2. Kena
3. Kaṭha
4. Praśna
5. Muṇḍaka
6. Māṇḍūkya
7. Taittirīya
8. Aitareya
9. Chāndogya
10. Bṛhadāraṇyaka
11. Brahma
12. Kaivalya
13. Jābāla
14. Śvetāśvatara
15. Haṃsa
16. Āruṇi
17. Garbha
18. Nārāyaṇa
19. Paramahaṃsa
20. Amṛtabindu
21. Amṛtanāda
22. Atharvaśira
23. Atharvaśikha
24. Maitrāyaṇi
25. Kauśītāki
26. Bṛhajjābāla
27. Nṛsiṃhatāpanī (purva)*
27. Nṛsiṃhatāpanī (uttara)*
28. Kālāgnirudra
29. Maitreya
30. Subāla
31. Kṣurika
32. Mantrikā
33. Sarvasāra
34. Nirālamba
35. Śukarahasya
36. Vajrasūchi
37. Tejobindu
38. Nādabindu
39. Dhyānabindu
40. Brahmavidyā
41. Yogatattva
42. Ātmabodha
43. Nārada­parivrājaka
44. Triśikhi-brāhmaṇa
45. Sītā
46. Yogachūḍāmaṇi
47. Nirvāṇa
48. Maṇḍala­brāhmaṇa
49. Dakṣiṇāmūrti
50. Śarabha
51. Skanda
52. Mahānārāyaṇa**
52. Tripādvibhuti-Mahānārāyaṇa**
53. Advayatāraka
54. Rāmarahasya
55. Rāmatāpaṇi
56. Vāsudeva
57. Mudgala
58. Śāṇḍilya
59. Paiṅgala
60. Bhikṣuka
61. Mahat
62. Śārīraka
63. Yogaśikhā
64. Turīyātīta
65. Sannyāsa
66. Paramahaṃsa­­parivrājaka
67. Akṣamālika
68. Avyakta
69. Ekākṣara
70. Annapūrṇa
71. Sūrya
72. Akṣi
73. Adhyātmā
74. Kuṇḍika
75. Sāvitrī
76. Ātmā
77. Pāśupata
78. Parabrahma
79. Avadhūta
80. Tripurātapani
81. Devī
82. Tripura
83. Kaṭharudra
84. Bhāvana
85. Rudrahṛdaya
86. Yogakuṇḍalini
87. Bhasmajābāla
88. Rudrākṣajābāla
89. Gaṇapati
90. Darśana
91. Tārasāra
92. Mahāvākya
93. Pañcabrahma
94. Prāṇāgnihotra
95. Gopālatāpani
96. Kṛṣṇa
97. Yājñavalkya
98. Varāha
99. Śāṭyāyani
100. Hayagrīva
101. Dattātreya
102. Gāruḍa
103. Kalisaṇṭāraṇa
104. Jābāli
105. Saubhāgya­lakṣmī
106. Sarasvatīra­hasya
107. Bahvṛca
108. Muktikā

* The Nṛsiṃhatāpanī listed in the Muktika Upanishad is found in some cases listed as two upanishads (the purva and the uttara). The total of 108 is reached when counting these as one, as is most common.

** This Upanishad exists in two main versions, with variations. Version 1 consists of either 64 or 80 chapters and is associated with the Krishna Yajurveda. Version 2 consists of 25 chapters, with the title prefix “Tripādvibhuti,” and is associated with the Atharvaveda. The Muktika, as translated by K. Narayanasvami Aiyar, lists “Mahānārāyaṇa” and associates it with the Atharvaveda.


Translations


See also:

The Mukhya Upanishads by Charles Johnston

The Principal Upanishads by Sarvepalli Radhakrishnan

Sechzig Upanishad’s des Veda (German) by Dr. Paul Deussen:
Sixty Upanishads of the Vedas (English Translation), Volume 1
Sixty Upanishads of the Vedas (English Translation), Volume 2

The [Principal] Upanishads by Swami Nikhilananda:
Volume 1: Katha, Isa, Kena, and Mundaka
Volume 2: Svetasvatara, Prasna, and Mandukya with Gaudapada’s Karika
Volume 3: Aitareya and Brihadaranyaka
Volume 4: Taittiriya and Chandogya

Eight Upanishads, with the Commentary of Sankaracharya by Swami Gambirananda:
Volume 1: Isa, Kena, Katha, and Taittiriya
Volume 2: Aitareya, Mundaka, Mandukya & Karika, and Prasna

The Principal [Mukhya] Upanishads with Shankara Bhashyas [Commentaries]:
Isa, Kena & Mundaka Upanishads with Shankara Bhashya, tr. S. Sitarama Sastri
Katha & Prasna Upanishad with Shankara Bhashya, tr. S. Sitarama Sastri
Chandogya Upanishad – Part 1 with Shankara Bhashya, tr. S. Sitarama Sastri
Chandogya Upanishad – Part 2 with Shankara Bhashya, tr. S. Sitarama Sastri
Aitareya & Taittiriya Upanishad with Shankara Bhashya, tr. S. Sitarama Sastri
Brihadaranyaka Upanishad with Shankara Bhashya, tr. Swami Madhavananda
Mandukya Upanishad with Gaudapada’s Karika and Shankara Bhashya, tr. Manilal N. Dvivedi

108 Upanishads with Sanskrit Commentary of Upanishad Brahma Yogin:
All Volumes (Sanskrit & English)
The Samanya Vedanta Upanishads, tr. Srinivasa Ayyangar
The Samnyasa Upanishads, tr. A. A. Ramanathan
The Sakta Upanishads, tr. A. G. Krishna Warrier
The Vaisnava Upanishads, tr. Srinivasa Ayyangar
The Saiva Upanishads, tr. Srinivasa Ayyangar
The Yoga Upanishads, tr. Srinivasa Ayyangar

The Upanishads by G.R.S. Mead and J.C. Chattopadhyaya:
Volume 1: Isa, Kena, Katha, Prasna, Mundaka, Mandukya
Volume 2: Taittiriya, Aitareya, Svetasvatara 

Oupnek’hat, Volume I, 1801, tr. Anquetil-Duperron (first western tr., Latin)
Oupnek’hat, Volume II, 1802, tr. Anquetil-Duperron (first western tr., Latin)


Selected Articles, Commentaries, etc.