Sarvāstivāda-Vaibhāṣika (Sanskrit: सर्वास्तिवाद-वैभाषिक) or simply Vaibhāṣika (वैभाषिक) was an ancient Buddhist tradition of Abhidharma (scholastic Buddhist philosophy), which was very influential in North India, especially Kashmir. In various texts, they referred to their tradition as Yuktavāda (the doctrine of logic), and another name for them was Hetuvāda (the doctrine of causes). The Vaibhāṣika school was an influential subgroup of the larger Sarvāstivāda school. They were distinguished from other Sarvāstivāda sub-schools like the Sautrāntika and the "Western Masters" of Gandhara and Bactria by their orthodox adherence to the doctrines found in the Mahāvibhāṣa, from which their name is derived (Vaibhāṣa is a vṛddhi derivative of vibhāṣa, meaning "related to the vibhāṣa"). Vaibhāṣika thought significantly influenced the Buddhist philosophy of all major Mahāyāna Buddhist schools of thought and also influenced the later forms of Theravāda Abhidhamma (though to a much lesser extent).

The Sarvāstivāda tradition arose in the Mauryan Empire during the second century BCE, and was possibly founded by Kātyānīputra (c. 150 BCE). During the Kushan era, the "Great Commentary" (Mahāvibhāṣa) on Abhidharma was compiled, marking the beginning of Vaibhāṣika as a proper school of thought. This tradition was well-supported by Kanishka, and later spread throughout North India and Central Asia. It maintained its own canon of scriptures in Sanskrit, which included a seven-part Abhidharma Piṭaka collection. Vaibhāṣika remained the most influential Buddhist school in Northwest India from the first century CE until the seventh century.

Despite numerous variations and doctrinal disagreements within the tradition, most Sarvāstivāda-Vaibhāṣikas were united in their acceptance of the doctrine of "sarvāstitva" (all exists), which says that all phenomena in the three times (past, present and future) can be said to exist. Another defining Vaibhāṣika doctrine was that of simultaneous causation (sahabhū-hetu), hence their alternative name of "Hetuvāda".

The main source of this tradition is the Sarvāstivāda Abhidharma Piṭaka.

The texts of the Sarvāstivādin Abhidharma Piṭaka are:

Together, these comprise the Six Treatises (Chinese: 六足論; Sanskrit: षड्पादशास्त्र, Ṣaḍ-pāda-śāstra). The seventh text is the Jñānaprasthāna ('Foundation of Knowledge'), also known as Aṣṭaskandha or Aṣṭagrantha, said to be composed by Kātyāyanīputra.

Yaśomitra is said to have likened this text to the body of the above six treatises, referring to them as its legs (pādas).

The Jñānaprasthāna became the basis for Sarvastivāda exegetical works called vibhāṣa, which were composed in a time of intense sectarian debate among the Sarvāstivādins in Kashmir. These compendia not only contain sūtra references and reasoned arguments but also contain new doctrinal categories and positions. The most influential of these was the Abhidharma Mahāvibhāṣa Śāstra ("Great Commentary"), a massive work which became the central text of the Vaibhāṣika tradition who became the Kashmiri Sarvāstivāda orthodoxy under the patronage of the Kushan Empire.